Detecting, Monitoring and Managing Enrichment of Streams

New Zealand
Periphyton Guideline:

Detecting, Monitoring and Managing Enrichment of Streams

Prepared for Ministry for the Environment
By Barry J F Biggs,
NIWA, Christchurch, June 2000

Foreword

New Zealand is a nation of water lovers. Nearly all of us have memories of tramping, fishing, swimming, picnics or holidays at rivers. Much of our adventure tourism industry also revolves around rivers. However, our modern lifestyle is placing increased pressure and stress on our rivers. Nutrients entering rivers and changes in flows can contribute to periphyton proliferation.

Periphyton is the slime and algae found on the beds of streams and rivers. It is essential for the function of healthy ecosystems, but when it proliferates it can become a nuisance, degrading swimming and fishing spots, clogging irrigation and water supply intakes.

When the Ministry published the first water quality guideline, Water Quality Guidelines No1: guidelines for the control of undesirable growths in water in 1992, it represented state-of- the-art information on managing nuisance biological growths in rivers and streams. However since then, not only has there been significant new research on the factors controlling periphyton, but there has been a significant shift in water management and periphyton is no longer managed as a problem but is also recognised as a key component of aquatic ecosystems.

This guideline has been developed collaboratively, with people from a range of agencies, including regional councils, Department of Conservation and Fish and Game New Zealand, providing valuable input. Our thanks go to all of the people who have made a contribution to the guideline. As a result of the collaborative, this guideline not only updates part of that first water quality guideline published in 1992, but also significantly expands the information covered. This is particularly important because it shows just how far we have come in water management in the nine years since the Resource Management Act 1991 was introduced.

We (Barry Biggs and the periphyton working group) have designed this guideline to help water managers determine the likely impacts of land and water developments on stream periphyton communities. It also provides tools to help them better manage the competing demands being placed on rivers.

This guideline needs to be used in the broader context of resource management and follow the approach first developed in the Flow Guidelines for Instream Values published in 1998. To this end, these guidelines are not a prescriptive recipe. They provide the information necessary for water managers to set objectives, evaluate and/or predict the natural condition of rivers and determine the appropriate management responses for individual situations.

I know that you will find these guidelines useful and that they will help you in the challenging task of water management in the 21st century.

Image 1

Denise Church

Chief Executive

Ministry for the Environment

Contents

Acknowledgements
Executive summary
1 Background and structure to Guidelines
1.1 Background
1.2 Purpose
1.3 Management approach suggested in Guidelines
1.4 Structure of Guidelines
2 Introduction to Guidelines
2.1 Responsibilities under the RMA and the relevance of stream periphyton
2.2 Habitat classification, periphyton and the management of streams
3 Periphyton and their importance in stream ecosystems
3.1 Terms
3.2 Phylogenetic links and general classification
3.3 Broad substratum-based community types
3.4 The benefits of periphyton in stream ecosystems
3.5 Values affected by nuisance growths
4 Review of factors most commonly controlling periphyton
growth and accumulation in streams
4.1 The hierarchy of environmental controllers
4.2 Overview of processes generating patterns in time and space
4.3 Time patterns
4.4 Spatial patterns
5 The effects of human activities on variables controlling periphyton growth
5.1 Hydrological disturbance
5.2 Nutrient supply
5.3 Light
5.4 Baseflow velocity
5.5 Baseflow temperature
6 Periphyton communities in New Zealand streams
6.1 Common periphyton communities in New Zealand streams
6.2 Unusual/unique/rare or endangered taxa or communities in New Zealand streams
6.3 Biomass
6.4 General biomass characteristics of periphyton communities in New Zealand streams
7 Periphyton as environmental indicators
7.1 Introduction
7.2 Biomass: Inorganic enrichment/trophic status
7.3 Autotrophic index: A measure of the degree of organic enrichment
7.4 Percentage organic weight
7.5 Indicator taxa: Organic enrichment
7.6 Indicator taxa: Inorganic enrichment/trophic status
7.7 Community diversity: a measure of the balance in population structure
7.8 Multivariate statistical analyses
7.9 Rapid assessment protocols
7.10 Functional responses
8 Guidelines for protecting instream values from enrichment effects
8.1 Suggested limits on amounts of periphyton for different instream values
8.2 Nutrient concentrations and biomass guidelines
8.3 Mitigation of periphyton proliferations if nutrient control is not possible
9 References .
Appendix I: Glossary

6

Periphyton communities in New Zealand streams

6.1 Common periphyton communities in New Zealand streams
6.3 Unusual/unique/rare or endangered taxa or communities in New Zealand streams
6.3 Biomass
6.4 General biomass characteristics of periphyton communities in New Zealand streams

7

Periphyton as environmental indicators

7.1 Introduction
7.2 Biomass: Inorganic enrichment/trophic status
7.3 Autotrophic index: A measure of the degree of organic enrichment
7.4 Percentage organic weight
7.5 Indicator taxa: Organic enrichment
7.6 Indicator taxa: Inorganic enrichment/trophic status
7.7 Community diversity: a measure of the balance in population structure
7.8 Multivariate statistical analyses
7.9 Rapid assessment protocols
7.10 Functional responses

8

Guidelines for protecting instream values from enrichment effects

8.1 Suggested limits on amounts of periphyton for different instream values
8.2 Nutrient concentrations and biomass guidelines
8.3 Mitigation of periphyton proliferations if nutrient control is not possible

9

References

Appendix I:

Glossary

Summary of Figures

 

Figure 1: The filamentous alga Vaucheria forming a rich green mat of periphyton over sands in a spring-fed stream near Pupu Springs, Takaka
Figure 2: General procedures for planning, setting consent criteria and verifying appropriateness of consent criteria for managing instream values in relation to periphyton (based on Figure 9 of the MfE Flow Guidelines (MfE, 1998))
Figure 3: Thick periphyton slimes on gravels, and mats of filamentous periphyton(Cladophora) caught around rocks, in a run of the Waipara River, North Canterbury
Figure 4: Scanning electron microscope photo of a silica frustule of the diatom Achnanthidium. The patterns of pores and etching on the surface are generally identical within a given species and are partly used in identification. A cell like this would normally need to be examined under a high-power microscope at >1000 X magnification to be certain of its identification. This species is widely found throughout the world and can adhere quite strongly to stones and macrophytes in streams. It is not normally associated with proliferations of periphyton
Figure 5: An aesthetically undesirable proliferation of filamentous green algae (mainly Oedogonium species) in a shallow gravel-bed river during summer low flows downstream of intensive agricultural development (Hakataramea River, North Otago). Enriched groundwater appeared to be entering the reach
Figure 6: Plume of filamentous green algae (Spirogyra) streaming from a groundwater upwelling at the side of a gravel-bed stream(Makara Stream, near Wellington)
Figure 7: A summary of the hierarchy of controllers of periphyton development and composition in streams. Strong causal effects are shown as solid arrows and weaker interactions are shown as dashed arrows. Double arrows indicate feedback relationships. Not all conceivable interactions are shown. For example, land use affects periphyton apart from through nutrients, notably with regard to riparian shading, but this interaction is not shown (modified from Biggs et al, 1990 with permission from New Zealand Journal of Marine and Freshwater Research)
Figure 8: Summary of the counteracting processes of periphyton biomass accrual and biomass loss, and the principal local factors contributing to these processes, in a stream. Triangles in the central rectangle show relative balance of “biomass accrual” and “biomass loss”. The growth form of the communities likely to dominate each end of the accrual Ð loss gradient is also shown (reproduced from Biggs, 1996a with permission from Academic Press)
Figure 9: An idealised short-term periphyton accrual cycle after major flooding. PB (peak biomass) = maximum accrual cycle biomass; TPB = time to PB from commencement of colonisation (reproduced from Biggs, 1996a
with permission from Academic Press)

Figure 10: Maximum recorded chlorophyll a biomass (~ peak biomass) versus mean monthly biomass of periphyton for 12Ð15 months of sampling at 30 New Zealand stream sites covering a wide range of enrichment (data derived from Biggs, 2000). Best-fit regression equation is: loge peak chlorophyll a (mg/m2) = 2.745 + 0.797 x loge (mean monthly chlorophyll a), r2 = 0.668, N =30
Figure 11: AFDM biomass of nine filamentous periphyton communities related to conductance (standardised to 25ûC) of the water in 400+ New Zealand streams during summer low flows. The error bars are 1Ês.d. (C. glomerata= Cladophora glomerata, M. varians = Melosira varians, U. zonata = Ulothrix zonata) (reproduced from Biggs and Price, 1987 with permission from the New Zealand Journal of Marine and Freshwater Research)
Figure 12: Peak biomass in diatom/Phormidium-dominated communities as a function of phosphorus supply concentration (as soluble reactive P) on natural rocks in artificial streams after three weeks. Biomass scale is in 200 mg chlorophyll a/m2 increments (reproduced from Welch, 1992 with kind permission from Kluwer Academic Publishers)
Figure 13: Maximum chlorophyll a as a function of mean monthly soluble inorganic nitrogen concentrations in 30 New Zealand streams (modified from Biggs, 2000 with permission from the Journal of the North American Benthological Society)
Figure 14: Maximum chlorophyll a concentrations as a function of mean days of accrual in 30 New Zealand rivers sampled every 2Ð4 weeks for at least 13 months (modified from Biggs, 2000 with permission from the Journal of the North American Benthological Society)
Figure 15: Log10 of maximum chlorophyll a (mg/m2) as a function of mean monthly soluble inorganic nitrogen concentrations and days of accrual (duration of stable flows). Calculated from Equation 1
Figure 16: Temporal variations in chlorophyll a (for a riffle community) and stream flows in the lower Kakanui River, North Otago (reproduced from Biggs et al, 1998b with permission from Archiv fŸr Hydrobiologie)
Figure 17: Three main community biomass responses to spatial variations in water velocity in streams
Figure 18: Mean monthly periphyton chlorophyll a as a function of flood disturbance frequency and enrichment (as mat % N concentration) (reproduced from Biggs, 1995 with permission from Freshwater Biology)
Figure 19: Armoured residual channel of the Tekapo River below the Lake Tekapo control gates during summer. Note the dominance of large cobbles and boulders on the surface layer
Figure 20: Proliferations of Cladophora in the Waipara River, North Canterbury downstream of seepage zones draining Tertiary marine sediments
Figure 21: Two contrasting treatments of stream environments in agricultural lands. The upper photo illustrates the destruction of habitat in first-order tributaries and how streams draining such areas can become silted and enriched. These small streams coalesce to form the bigger streams and rivers so are the first place to start with habitat protection measures. The lower photo illustrates good farming practice with the preservation of vegetation cover around a first-order stream
Figure 22: Location of common New Zealand stream and river types on a habitat matrix defined by gradients in flood disturbance frequency and nutrient enrichment
Figure 23: Dark skein of interwoven Phormidium filaments over thick mucilage on a cobble
Figure 24: Clouds of Spirogyra in a spring-fed pool near the Hawdon River, Arthurs Pass National Park
Figure 25: Cumulative frequency curves for chlorophyll a and ash-free dry mass from unenriched/oligotrophic sites (squares), moderately enriched/ mesotrophic sites (triangles), and enriched/eutrophic sites (dots) in New Zealand streams sampled every 4 weeks for a year (data pooled for groups of sites in each enrichment category with N = 4, 6, and 6 sites respectively; see Biggs, 1995 for sampling and site information). The dashed lines denote the 25th, 50th and 75th percentiles (reproduced from Biggs, 1996a with permission from Academic Press).
Figure 26: Example of the results of a nutrient diffusing substrate experiment in a hill country river (Kauru River, Otago). Vertical bars denote standard errors
Figure 27: Stone with a thick diatom mucilage dominated by Gomphoneis and Cymbella. The olive green filaments are formed by the chain-forming diatom Fragilaria, Baton River, Northwest Nelson.
Figure 28: Gradient in percentage cover and biomass of filamentous algae, Waipara River, North Canterbury
Figure 29: Relative abundance of Òclean waterÓ EPT invertebrates (Ephemeroptera (mayflies), Plecoptera (stoneflies), Trichoptera (caddisflies)) as a function of the ash-free dry mass of periphyton in the samples. The line of Òbest-fitÓ was determined using distance-weighted least squares regression. Most
periphyton samples were dominated by diatoms (Gomphoneis, Cymbella, Synedra) and filamentous cyanobacteria (Phormidium).
Figure 30: Nomograph of mean monthly soluble nutrient concentrations that are predicted to result in maximum benthic algal biomass indicative of oligotrophic, mesotrophic, and eutrophic conditions for varying days
of accrual (da) in gravel/cobble-bed streams. The oligotrophic Ð mesotrophic boundary was set at 60 mg/m2 chlorophyll a and the mesotrophic Ð eutrophic boundary was set at 200 mg/m2 chlorophyll a
(after Dodds et al. 1998). These boundaries approximate the maximum biomass criteria adopted for the protection of benthic biodiversity (oligo- to mesotrophic), aesthetics, and trout fishery values (meso- to eutrophic) (see Table 14 page 102). The lines delineating the trophic boundaries were calculated using the soluble inorganic N (SIN) equation on page 43. However, these lines also approximate boundaries for P-limited communities by reference to the right-hand scale, which has been set at 0.1 x the SIN scale, because the mean ratio of biomass from the SIN and soluble reactive P (SRP) models was 10.8. The left-hand (SIN) axis is used for nitrogen limited communities and the right-hand axis (SRP) is used for phosphorus limited communities.

Summary of Tables

Table 1: Summary of the main divisions of algae found in stream periphyton communities, their morphology and means of motility (after Bold and Wynne, 1985; Stevenson, 1996a) (Mot., motile; N-M, not motile).
Table 2: Summary of common subgroups of periphyton based on the nature of the substratum that they colonise (based on Burkholder, 1996; Stevenson, 1996a, S.ÊMoore pers. comm.)
Table 3: Instream values that can be compromised and associated problems that may arise as a result of periphyton proliferations (based on MfE 1992 and Biggs, 2000)
Table 4: Primary variables controlling periphyton community biomass accrual, general human activities that may influence these variables and the overall effects on periphyton biomass in shallow, stony streams
Table 5: Summary of the ÒcoreÓ periphyton taxa of New Zealand streams and rivers (derived from Biggs and Price, 1987; Biggs, 1990a) (*, denotes taxa forming macroscopically distinctive communities which can be identified in the field when developed as a thick mat
Table 6: Periphyton communities commonly found in New Zealand streams and rivers of different trophic state
Table 7: Statistics for chlorophyll a and AFDM biomass distributions calculated from monthly samples for a year in four oligotrophic, six mesotrophic and six eutrophic gravel/cobble bed New Zealand
streams (based on Biggs, 1995).
Table 8: Gross water quality characteristics and associated periphyton communities along a river receiving organic enrichment according to the European Saprobic system (from Fjerdingstad, 1964).
Table 9: Trophic designations of some taxa commonly found in New Zealand periphyton communities (developed from Biggs and Price, 1987; Biggs, 1990a, 1995; Kelly and Whitton, 1995; Biggs et al, 1998d; Biggs,
unpublished data; S.ÊMoore, unpublished data). Note that the habitats listed for each taxon are where that taxon is most likely to dominate communities or be abundant. However, many taxa (particularly diatoms), can be found as subsidiary components of mats in other environments.
Table 10: Multivariate analyses commonly used in ecological studies and biological monitoring/ resource assessments. This is not an exhaustive list
Table 11: Suggested criteria from various studies for maximum periphyton biomass to avoid problems for recreational and aesthetic use of streams (from Dodds et al, 1998).
Table 12: Relative abundances of main invertebrate groups in New Zealand streams according to trophic state (data derived from Quinn and Hickey 1990, and Biggs 1995). The invertebrate data is from one sampling
(seven replicates) in late summer
Table 13: Maximum and geometric mean (~ median) monthly chlorophyll a concentrations from some reaches of New Zealand rivers renowned for their trout fisheries. Maximum values are based on transects across
reaches and are the highest recorded average transect biomass. Most communities at the time of high biomass were dominated by diatoms (principally Gomphoneis minuta var. cassieae and Cymbella
kappii) and filamentous cyanobacteria (principally Phormidium).
Table 14: Provisional biomass and cover guidelines for periphyton growing in gravel/cobble bed streams for three main instream values
Table 15: Maximum soluble inorganic nitrogen (SIN = NO3 Ð N + NO2 Ð N + NH4 Ð N) and soluble reactive
phosphorus (SRP) supply concentrations (mg/m3) necessary to prevent maximum periphyton biomass from exceeding the given levels as derived from: 1) experimental studies with phosphorus limited periphyton in the absence of disturbance, and 2)Êregression equations 1 and 2 (see Section 4.3.3) from nutrient biomass relationships in New Zealand streams with varying lengths of accrual time. The nutrient concentrations
in Part II of the table were determined as mean monthly concentrations over a year. Limits of detection are assumed to be around 5 mg/m3 for SIN and 1 mg/m3 for SRP if routine analyses are carried out using standard autoanalyser techniques. SIN concentrations in italics were calculated from the limiting SRP concentration assuming an N:P ratio (by weight) for optimum growth in algae of 7.2:1 (Welch, 1992). The chlorophyll a at 120 mg/m2 refers to filamentous green algae dominated communities whereas the chlorophyll a at 200Êmg/m2 refers to diatom dominated communities. Chlor. a = chlorophyll a (mg/m2); AFDM = ash-free dry mass (g/m2).

Acknowledgements

I am grateful for the many suggestions and review comments from Maurice Rodway (Southland Fish and Game Council), Steve Moore (Otago Regional Council), Philippe Gerbeaux (DoC), John Hayes (Cawthron Institute), Alastair Suren (NIWA), John Quinn (NIWA), John Philips (Horizons.mw), Ellen Forch (Hawkes Bay Regional Council), Brett Stansfield (Wellington Regional Council), Ian Hawes (NIWA), Hamish McWilliam (Taranaki Regional Council), Keith Hamill (Southland Regional Council) and Kit Rutherford (NIWA). I am also grateful for the assistance of Ruth Berry (Ministry for the Environment) in preparation of Section 2 and for administering the publication of this manual.

While drawing on information from the international literature, the core of this manual is based on extensive research carried out in New Zealand and funded through the Public Good Science Fund (most recently through the NIWA programmes “Environmental Hydrology and Habitat Hydraulics” and “River Ecosystems – Land Use Interactions”) and also the Department of Conservation. This funding has been greatly appreciated and enabled me (and several of my colleagues) to start to unravel and understand some of the complexity of factors controlling periphyton development in streams and rivers of New Zealand. Through these Guidelines, I am hopeful that this knowledge will now be more widely available and benefit water management, the public, and stream ecosystems generally. The preparation of the Guidelines was funded by the Ministry for the Environment.

Executive summary

Periphyton is the slime and algae found on the bed of streams and rivers. This group of organisms is essential for ecosystem functioning but under certain circumstances can proliferate, causing water resources management problems such as degrading aesthetic, recreational and biodiversity values. Proliferations can also taint water, be toxic to animals, and clog abstraction intakes. New Zealand streams are particularly prone to such proliferations because of the gravel/cobble nature of the beds, high-intensity sunlight, warm waters and enrichment from natural and anthropogenic causes (eg, nutrient-rich rocks, agricultural land use). Thus, periphyton communities should be considered as a possible issue in any planning or resource assessments involving streams and rivers. Indeed, under the Resource Management Act 1991 (RMA), regional councils have the responsibility for ensuring that the life-supporting capacity of the environment is maintained but that nuisance growths of organisms are not enhanced. These Guidelines are designed to help water managers determine the likely impacts of land and water developments on stream periphyton and thus assist to facilitate the intent of the RMA.

This Guideline gives a background review of the structure and value of periphyton communities in streams, factors controlling growth and composition of periphyton, and the effects of human activities on the community. A set of guidelines is then developed to help prevent degradation of aesthetic/recreational, biodiversity and angling values by excessive enrichment of streams (and resultant proliferations of periphyton). The biomass and cover guidelines are summarised below.

Provisional biomass and cover guidelines for periphyton growing in gravel/cobble bed streams for three main instream values (AFDM = ash-free dry mass).
page-12-image
The percentage cover values apply to the part of the bed that can be seen from the bank during summer low flows (usually <0.75 m deep) or walked on. The biomass guidelines are expressed in terms of biomass per unit of exposed substrata (ie, tops and sides of stones) averaged across the full width of the stream or river in a reach. A reach is defined as a relatively homogeneous section of stream channel. Most commonly this will be a run, but this should be clearly specified in setting consent conditions. For maintenance of benthic biodiversity (ie, a "clean-water" benthic fauna), the guidelines are given in terms of mean monthly and maximum chlorophyll a. The aesthetics/recreation guidelines are only expected to be applied over the summer months (1 November - 30 April). Relationships are also developed between peak biomass of periphyton and the primary controlling variables of time available for growth (ie, time between flood events) and nutrient concentrations in the water (as mean monthly concentrations measured over at least a year). These relationships are then used to develop nutrient guidelines for various growth periods to ensure that peak biomass doesn't exceed the biomass guidelines for the various instream values as summarised below. Soluble inorganic nitrogen (SIN = NO3 – N + NO2 – N + NH4 – N) and soluble reactive phosphorus (SRP) concentrations (mg/m3) predicted to prevent maximum biomass from exceeding the given levels. The nutrient concentrations are to be determined as mean monthly concentrations over a year. Limits of detection are assumed to be around 5 mg/m3 for SIN and 1 mg/m3 for SRP if analyses are carried out using standard autoanalyser techniques. The chlorophyll a at 120 mg/m2 refers to filamentous green algae dominated communities whereas the chlorophyll a at 200 mg/m2 refers to diatom dominated communities. AFDM = ash-free dry weight.
page-13-image
In using the soluble inorganic nutrient guidelines for developing consent conditions, it is important to recognise that the specific nutrient limiting periphyton growth needs to be identified and consent conditions set in terms of that single nutrient. It is usually unnecessary to specify conditions in terms of both nitrogen and phosphorus. One of these nutrients will generally be in surplus and therefore at much higher concentrations than the guideline shown in the above table. Also, it is important that the background soluble nutrient concentrations coming into the reach of interest are evaluated thoroughly. This will usually involve monthly sampling for a year to characterise temporal dynamics and get an estimate of the mean concentrations. This will provide the basis for nutrient supply calculations associated with any discharges in relation to the instream management objective and associated guideline biomass.

A number of mitigation options are discussed in the event that nutrient control to reduce the potential for proliferations is not feasible. These include riparian shading, artificial flushing events in regulated rivers, and optimising benthic invertebrate habitat to increase losses through grazing activity.

The technical manual details methods for surveying and sampling periphyton, analysis of biomass (ash-free dry mass and chlorophyll a), and analysis of the taxonomic composition of the communities.

The present Guidelines do not cover proliferations caused by sewage fungus. The 1992 Ministry for the Environment Water Quality Guidelines #1 are still current for those communities.

1 Background and structure to Guidelines

1.1 Background
Periphyton is found in all aquatic habitats but is often most conspicuous in streams and rivers. Periphyton is the slime coating stones, wood, weeds or any other stable surfaces in streams. The community may sometimes be difficult to detect, but gives these surfaces a brown or brown-green colouring. Scrape a stone in a stream and the pile of brown material that accumulates will be periphyton. In some situations it can proliferate and form clouds or mats of green or brown filaments over the stones or in pools. This is when periphyton is at its most conspicuous (Figure 1).

Figure 1: The filamentous alga Vaucheria forming a rich green mat of periphyton over sands in a spring-fed stream near Pupu Springs, Takaka.
page-15-image

The periphyton community is fundamental for sustaining life, affecting natural character and determining the intrinsic values of stream ecosystems. Indeed, this community contains the main primary producers of streams, the transducers of light energy and mineral nutrients into food for most other forms of stream life. Thus, the effects should always be evaluated on the form, quantity and functioning of periphyton communities of any developments involving the use of water from streams or changes in stream channel structure.

In 1992, the Ministry for the Environment published the document Water Quality Guidelines No. 1: Guidelines for the control of undesirable growths in water (MfE, 1992) . When published, those Guidelines represented the state of the art in matters concerning controlling nuisance biological growths in streams and rivers. The 1992 Guidelines covered sewage fungus, phytoplankton, periphyton and macrophytes. However, since then there has been significant new research on periphyton and the factors controlling its growth. These new Guidelines therefore focus just on periphyton, taking advantage of much of this new research to develop an updated set of tools and understandings that will improve our ability to manage periphyton growth in streams.

1.2 Purpose

The purpose of this guideline is to provide an objective way of managing periphyton in streams, both for its important primary production role in ecosystems and for managing nuisance proliferations. These Guidelines do not provide any direction on resolving competition between instream values such as trout habitat and out-of-stream uses such as abstraction. This competition must be resolved on a case by case basis, using the following to guide the decision – Parts II, III, IX and Schedule III of the Resource Management Act 1991(RMA), regional policy statements, regional plans and consultation with communities of interest.

These Guidelines are not a prescriptive recipe. They provide the information necessary for users to set objectives, evaluate and/or predict the natural conditions and determine appropriate management responses for individual situations.

1.3 Management approach suggested in these Guidelines

Effective management requires clear and measurable goals so that progress can be assessed. You must know what you are managing your waterway for. The recommended approach for managing periphyton used in these Guidelines, as shown in Figure 2, provides a framework for identifying values, setting objectives and monitoring the effects of management responses. It is the same approach used in the Flow Guidelines for Instream Values (MfE, 1998). The process as it relates to periphyton is as follows:

  1. Identify instream and out-of-stream values for the water resource concerned (eg, irrigation, contact recreation, particular fish or bird habitat).
  2. Use a classification of physical features to determine whether values are compatible with the natural physical constraints of the system. For example, if the local geology is dominated1 by nutrient-rich Tertiary marine siltstones, filamentous algal blooms are likely to occur naturally.
  3. Note: The 1992 Guidelines remain current for sewage fungus and the impact of organic contamination. Those issues are not covered in these revised periphyton Guidelines.

    The use of the word “dominated” in this context does not imply that a characteristic is present in proportions greater than 50 percent. Rather, “dominant” means that a characteristic is present in proportions large enough to be the predominant controller of instream responses.

  4. Determine instream management objectives (ISMOs) for identified values, such as:
  5. A. Maintain instream conditions which allow Grade 3 whitewater rafting over the summer rafting season (1 November – 30 April).
    B. Maintain instream conditions which allow passage of salmon during the period 1 January – 1 May.
    C. Maintain instream conditions of <30 percent cover of filamentous algae in order to allow swimming over the summer (1 November - 30 March). D. Allow no degradation of benthic invertebrate communities currently comprised of >50 percent Ephemeroptera + Plecoptera + Tricoptera taxa.
    E. Maintain trout habitat at a level which will allow at least 0.3 fish per square metre in the following rivers etc.

    To be most effective, ISMOs should be defined in terms of space and time and specify a level of protection. In the above examples, defining where an ISMO applies could be by way of including a description of the area in the ISMO itself, or it could be linked to regional classification maps etc. The level of protection is signified by specific measurable degrees such as “… allow Grade 3 whitewater rafting …” or “… benthic invertebrate communities currently comprised of >50 percent Ephemeroptera …”.

    Levels of protection are important qualifiers for ISMOs. They give added flexibility in the way systems are managed with the result that a greater range of values and end-uses can potentially be catered for. Using levels of protection also results in clearly measurable objectives. Levels of protection do, however, highlight the need for good, defensible, relationships or models to enable accurate predictions to be made of the effects of more subtle changes in water management regimes (and thus controlling parameters) on periphyton biomass and community composition.

  6. Decide whether periphyton is likely to be an issue for any identified values or ISMOs (given the habitat type of the stream or river). Using the above example, periphyton has the potential to be a nuisance in ISMO C whereas for ISMOs D and E, periphyton will be important for ecosystem maintenance. Periphyton is unlikely to be of major concern for ISMOs A and B.
  7. Using ISMOs and habitat type information select appropriate parameters, methods and sites for monitoring. For example, for ISMO C, the parameter would be periphyton biomass. The sample-collection method is habitat-dependent, such as scraping the community from a set area for gravel/cobble-bed streams.
  8. If monitoring results indicate that suitable boundaries or levels are being exceeded, appropriate management action needs to be taken – for example, reviewing resource consent conditions.

Figure 2: General procedures for planning, setting consent criteria and verifying appropriateness
of consent criteria for managing instream values in relation to periphyton (based on Figure 9 of the Flow Guidelines for Instream Values (MfE, 1998)).

page-18-image

2 Introduction to Guidelines

Of key concern to water managers, iwi, recreationalists, conservationists and the general public are the “instream values” of our rivers. The Flow Guidelines (MfE, 1998) define instream values as including:

  • ecological values
  • aesthetic values (including recreational and landscape values)
  • values linked with Maori culture and tradition.

When managing rivers and streams for instream values, it is important to consider periphyton for two reasons: periphyton provides much of the energy for the maintenance of the rest of the ecosystem, right through to fish. Therefore, it is essential that we ensure that a healthy, diverse periphyton community exists if we wish to have a healthy and diverse stream ecosystem. Such attributes are also necessary to meet the cultural expectations of a society increasingly sensitive to environmental quality and sustainable resource use. Second, periphyton can proliferate, forming large nuisance growths of slime. Such growths can interfere with human uses and degrade the habitat for other organisms. While high biomass is a natural phenomenon in many streams at certain times of the year, human activities can easily increase both the size of the growths and the length of time over which they occur in streams.

2.1 Responsibilities under the RMA and the relevance of stream periphyton

Water management in New Zealand is principally controlled by the RMA. Section 5 of the RMA describes its purpose:

  1. The purpose of this Act is to promote the sustainable management of natural and physical resources.
  2. In this Act, “sustainable management” means managing the use, development and protection of natural and physical resources in a way, or at a rate, which enables people and communities to provide for their social, economic and cultural well being and for their health and safety while –

a Sustaining the potential of natural and physical resources (excluding minerals) to meet the reasonably foreseeable needs of future generations; and

b Safeguarding the life-supporting capacity of air, water, soil and ecosystems; and

c Avoiding, remedying or mitigating any adverse effects of activities on the environment.

Further analysis of section 5 and its meaning can be found in the Flow Guidelines for Instream Values, Volume A (MfE, 1998).

Under section 30 of the RMA, functions and powers for water management lie with regional councils. Regional councils may prepare regional plans for water (and other natural and physical resources) to assist with carrying out their functions under the RMA.

This is particularly important for water management, as the restrictions placed on water and the beds of rivers and lakes mean that most activities are prohibited unless they are expressly allowed by a rule in a regional plan or resource consent.

The RMA requires that all components of ecosystems and human needs be addressed. Section 6, on matters of national importance, includes the need to consider and preserve the natural character of rivers and their margins (6(a)) and the protection of areas of significant indigenous vegetation and significant habitats of indigenous fauna (6(c)). Section 7 instructs that particular regard must be taken of the “intrinsic values” of a system (ie, its biological diversity and the essential characteristics which determine an ecosystem’s integrity, form, functioning and resilience (7(d)), maintenance and enhancement of the quality of the environment (7(f)) and the protection of trout and salmon (7(h)).

In certain circumstances periphyton can proliferate and become a nuisance and adversely affect water quality for a range of instream values. The RMA provides for waters to be classified in regional plans as an aid to the management of water quality. In recognition of the potential problems created by high-biomass biological growths in streams, the RMA specifies the following standard for waters being managed for aquatic ecosystem purposes, fish spawning, contact recreation, water supply, irrigation and industrial abstraction: “There shall be no undesirable biological growths as a result of any discharge of a contaminant into water” (Schedule III).

These Guidelines are intended to assist water managers in carrying out their functions under the RMA and in the application of the standards for water classes in Schedule III. The suggestions presented will allow water managers to more easily identify areas where periphyton has the potential to proliferate, form nuisance growths, and to control such growths.

2.2 Habitat classification, periphyton and the management of streams

Streams and rivers, and the ecosystems they support, are controlled by a hierarchy of physical variables. At the broad scale, different combinations of the ultimate variables of the environment- geology, climate and human activities and the subsidiary outcome of these such as topography, slope, vegetation and land use – are the fundamental controllers of local habitats for stream biota as measured by variables such as depth, velocity, nutrients, etc (Biggs et al, 1990). Different combinations of these variables result in specific types of habitats such as shallow, swift cobble-bed streams with unenriched waters or deep, slow-moving streams with silty beds that may be enriched. Different sets of biota, including periphyton, have evolved to exploit such differences in habitat conditions. Classifying these different habitats using an appropriate set of controlling variables, and defining distinctively different biological communities in these different habitat types, has a number of advantages for water resource management (Biggs et al, 1997b; Snelder et al, 1998):

  • setting ISMOs: a framework for assessing human values associated with a particular stream, resolving conflicts between values, then setting management objectives at local and regional levels. Reference to the habitat type also assists in identifying the variables requiring monitoring for achieving the given objectives (eg, nutrient
    concentrations)
  • prediction: community composition and biomass likely to be encountered in areas where information is lacking can be predicted by analogy to similar habitat types where information does exist
  • setting conditions in statutory planning: a framework for setting regionally relevant and achievable water quality and biological conditions
  • bio-assessment: a basis for comparing and interpreting the state of biological communities, and thus the relative health of stream ecosystems, regionally and nationally such as for state of the environment reporting
  • monitoring: to help define reference sites and develop monitoring programmes
  • methods: to help decide on sampling methods
  • data interpretation: encouraging the development of a holistic approach to river management, highlighting the linkages between physical and biological responses and the need to consider multiple trophic levels.

One of the most important benefits of using physical habitat classification as a basis for evaluating periphyton communities (and indeed stream management in general) is that through the association of specific biological communities with specific habitat types, there is a more objective basis for evaluating potential instream values and then managing public expectations. It is very important that the public’s expectations are realistic. However, there are many cases in which they aren’t. Habitat classification helps us identify such situations. For example, people might want to have a particular section of a stream managed for recreational fishing, and for this to happen, it might be necessary to eliminate blooms of filamentous algae during summer. However, if the catchment includes a significant proportion of Tertiary marine siltstones which are rich in nutrients, this would be readily detected in the habitat classification. It would then be clear that filamentous algal growths are a natural product of the catchment conditions and clearly impossible to control.

3 Periphyton and their importance in stream ecosystems

3.1 Terms

Periphyton, as noted earlier, is the slime coating objects in streams. Occasionally difficult to detect, periphyton colours submerged objects brown or green (see Figure 3). The term periphyton is the most common descriptor in stream ecology for this community. However, other terms are also used, such as Aufwuchs (commonly used in Europe), a German description of the community meaning “to grow upon” (Stevenson, 1996a), and phytobenthos. The community is composed predominantly of algae and cyanobacteria (previously called “blue-green algae”) and so the term benthic algae is also used (particularly by algal biologists). The term periphyton is adopted for the present guide since it has become the most widely used term in stream ecology.

Figure 3: Thick periphyton slimes on gravels, and mats of filamentous periphyton (Cladophora) caught around rocks, in a run of the Waipara River, North Canterbury.
page-22-image
The term periphyton community is commonly used throughout the guideline. This denotes a specific group of periphyton taxa. Often the individuals of such groups will not be closely related phylogenetically but have developed traits independently that allow them to coexist in the same habitat. For example, the filamentous cyanobacterium Phormidium can overlie communities dominated by diatoms (such as Cymbella, Gomphoneis and Synedra) in slow-flowing habitats of moderately enriched streams in late summer.

Population refers to many individuals of just one species. A major problem in periphyton evaluation is that many of the organisms cannot be identified to species level because, for example, they lack the necessary reproductive structures at the time of analysis. As a result just the generic level name is often only used. This commonly occurs for the filamentous green algae. The term taxa (singular: taxon) refers to an organism identified to its lowest practical taxonomic level.

While periphyton are present in all streams and rivers, these Guidelines will mainly concentrate on communities living in relatively shallow streams/rivers (ie, wadable) which have beds predominantly composed of gravels and cobbles. These are the environments where periphyton impact most on human values and contribute most to aquatic food chains. Such streams are commonly found throughout New Zealand draining areas of foothills and mountains. In lowland areas, or in areas with a very low gradient, streams tend to have low energy, the bed sediments are mainly composed of silts/sands, flow variability is low and primary production in such streams tends to be dominated by larger vascular macrophytes or phytoplankton.

A glossary of terms commonly used in the manual is given in Appendix 1.

3.2 Phylogenetic links and general classification

While most algal taxa in the periphyton obtain their energy for growth through photosynthesis (a distinguishing character of plants), a number of scholars do not consider these organisms to be plants. Indeed, only one Division (the ÒgreenÓ algae) are true plants in the evolutionary sense, whereas another is composed of bacteria and more closely related to animals (popularly known as the Òblue-green algaeÓ, but more correctly termed cyanobacteria) (Lowe and Lalibertae, 1996).

Different groups, or divisions, of algae in the periphyton community are distinguished primarily on the basis of their pigmentation. All divisions have chlorophyll a; however, some divisions have other pigments such as b, c, or d. Other accessory pigments such as fucoxanthin may be prominent, and these accessory pigments may give some divisions their
distinctive coloration such as in the red algae. There are also important differences in the composition of cell walls and storage products. For a more comprehensive summary of the basis for taxonomic division of periphyton communities and algae in general, see Stevenson(1996a) and Bold and Wynne (1985).

Table 1: Summary of the main divisions of algae found in stream periphyton communities, their morphology and means of motility (after Bold and Wynne, 1985; Stevenson, 1996a) (Mot., motile; N-M, not motile).
page-24-image

While the different Divisions of algae comprising stream periphyton communities are mainly distinguished on differences in pigmentation, these are usually accompanied by conspicuous differences in size of filaments, texture, shape of cells etc. This enables the groups to be distinguished in the field with the naked eye or with the assistance of a simple low-powered field microscope. Some taxa are even distinguishable in the field down to the generic level. However, fine-scale identification to genus and species levels is mostly carried out on the grounds of detailed cell size and morphology (eg, morphology of the silica frustules that make up the internal structure of diatoms), branching patterns (eg, some green and red algae), and reproductive structures (eg, cyanobacteria, green algae and red algae). Such characteristics can only be distinguished using detailed microscopy.

Four main morphological types can be distinguished: filamentous unbranched, filamentous branched, unicellular and colonial/multicelled (see technical manual). Most diatoms are unicellular (eg, species of Navicula, Synedra), a few diatoms and some cyanobacteria are colonial (eg, Fragilaria, Nostoc), and most green and red algae are filamentous (eg, Stigeoclonium, Audouinella) (Table 1). Reproductive structures are particularly important in distinguishing different species of filamentous green algae. However, these structures are rarely present (because reproduction is usually vegetative in these taxa), so we are seldom able to characterise communities dominated by filamentous green algae to species level (eg, Spirogyra, Oedogonium).

Similarly, many species of cyanobacteria are partly distinguished on the basis of characteristics such as the thickness of layers of mucilage surrounding individual filaments, and these are very difficult to discern without special staining and a very high degree of experience (eg, Lyngbya, Phormidium). The use of size and morphology for separating species and genera presents difficulties (particularly within the diatoms). This is because there is a high degree of variability and many so-called “species” appear to grade into other species depending on the habitat. Even within a given habitat and sample there can be wide variations in size associated with differences in the state of vegetative reproduction. For example, diatoms get progressively smaller as a given population continues to divide until they reach a certain “minimum” size after which sexual reproduction occurs and a group of full-sized individuals can redevelop.

Most of the Divisions have genera that have cells or filaments that move (called “trichomes” in the cyanobacteria) (Table 1). This is an attribute of these communities that is unusual for “plant-like” organisms. Trichomes of Oscillatoria can often be seen “gyrating” under the microscope. Some unicellular diatoms are also highly motile. These are mainly raphed forms such as Navicula and Frustulia. They can move at amazing speed, covering distances many times their body length in minutes (equivalent to approximately 1 m/h) and can be observed while examining virtually any fresh samples under a high-powered microscope (ie, 1000 X magnification). Some larger taxa gather enough momentum to knock other taxa off the substrate. Motility allows these taxa to move up to the surface of the mat in search of light and nutrients and also allows them to burrow down to the base of the mat in times of adversity. Such a facility is very advantageous in sand habitats where it appears that these taxa may actively burrow to evade the abrasive effects of higher water velocities.

3.3 Broad substratum-based community types

A fundamental controller of the nature and general taxonomic composition of periphyton communities in streams is the type of substratum that the community grows on (eg, sand vs. stones vs. weeds etc.; Burkholder, 1996). This is a function of micro-spatial differences in habitat stability (~ disturbance) and nutrient resource supply that vary over small spatial scales in streams. Different groups have evolved specific attributes that enable them to exploit certain combinations of habitat stability and resource supply more successfully. A summary of commonly recognised subgroups of periphyton is given in Table 2.

Table 2: Summary of common subgroups of periphyton based on the nature of the substratum that they colonise (based on Burkholder, 1996; Stevenson, 1996a, S.ÊMoore pers. comm.).

page-26-image

Taxa on rock and larger plant habitats are generally well attached by mucilaginous pads (eg, Synedra ulna), as a part of mucilage mounds or balls (eg, Nostoc), by mucilaginous stalks (eg, Gomphoneis), by specialised holdfast structures (eg, Ulothrix), or by entanglement in other well-attached taxa (eg, Melosira varians). Taxa dominating sand and mud habitats are often quite motile. Many of these taxa may also be found abundantly among the more firmly attached rock communities. Indeed, several of the rock based taxa are also not particularly specific in their substrate requirements. For example, the filamentous red alga Audouinella hermanii is often found on stable boulders and embedded cobbles/gravels, but can also form very conspicuous epiphytic communities on aquatic mosses and submerged willow roots (Biggs and Price, 1987). Similarly, the diatoms Achnanthidium minutissimum and Cocconeis placentula can be found abundantly in both epilithic and epiphytic habitats.

3.4 The benefits of periphyton in stream ecosystems

As noted earlier, periphyton is the primary transducer of the sunÕs rays into biologically based energy for stream ecosystems. Thus, this community is the ÒgrassÓ of streams for aquatic grazing animals. Take the periphyton away and we would often only have barren flow chutes, devoid of insects and fish. In some northern hemisphere forest streams, inputs of palatable leaf detritus can be high (eg, from deciduous trees) and many stream insects have evolved to utilise this energy source. However, in New Zealand this link is less clear and, at least for streams in unforested catchments (probably the majority of our larger streams and rivers), the energetics of ecosystems appear to be more driven by instream “autotrophic production”.

A major portion of the periphyton in streams is composed of algae. These algae capture the energy of sunlight via their chlorophyll molecules, absorb carbon dioxide and other nutrients such as phosphorus and nitrogen from the surrounding water, and then synthesise organic carbon in the form of new or enlarged cells. Algae commonly secrete a portion of this
carbon, and a host of other organisms then live off this material such as communities of bacteria, fungi and protozoa. Indeed, large algal filaments are often substrates for smaller algal filaments or unicellular algae (Figure 4), and cells which are then substrates for bacteria.

Figure 4: Scanning electron microscope photo of a silica frustule of the diatom Achnanthidium. The patterns of pores and etching on the surface are generally identical within a given species and are partly used in identification. A cell like this would normally need to be examined under a high-power microscope at >1000 X magnification to be certain of its identification. This species is widely found throughout the world and can adhere quite strongly to stones and macrophytes in streams. It is not normally associated with proliferations of periphyton.

page-28-image

This micro- and macroscopic assemblage is then grazed by the invertebrates (snails, mayflies, caddisflies, midges etc) that live on the stream bed. These invertebrates usually hide under the stones for much of the day, venturing out onto the rocks to graze the periphyton mat in darkness. Some insects such as midges even burrow into the periphyton and make tube dwellings within the mat.

While few invertebrates appear to have become specialised in grazing certain forms of periphyton, the best periphyton for most invertebrates appears to be composed of diatoms. These are generally high in fats and oils (lipids) and are also easily grazed because they usually only form moderate to thin films on stones. Some invertebrate species appear to avoid some of the large, green filamentous algae. This may be because the diameter of the filaments is too great for the grazers to take into their mouths, these species may have too little food value, or they may have anti-herbivory chemicals that render them unpalatable.

Another important role for periphyton in streams is its ability to improve water quality. Indeed, these communities are cultivated in trickling filters of wastewater treatment plants to remove pollutants and polish effluent prior to discharge. In shallow streams, natural periphyton communities act in a similar way. They have a high capacity for removing nitrogen and phosphorus from stream waters, and the bacterial communities within mats have a great ability to remove organic contaminants (eg, from farm stock and surface runoff from the land). This process then makes the water much more useable for other purposes such as stock drinking supplies. The contaminating nutrients, accumulated as periphyton biomass, are often flushed out of the stream system during floods.

3.5 Values affected by nuisance growths

Problems associated with excess biomass accumulation (nuisance growths) tend to become most prominent during low flows (Figure 5) and thus tend to be sporadic. Some common stream-related values that may be compromised by periphyton proliferations, and the associated problems, are listed in Table 3. The extent of the annoyance created by proliferations to aesthetic appreciation, angling, contact recreation such as swimming, and whitebait fishing is very subjective and likely to vary greatly among individuals and also as a function of the type of stream environment. The effects on water quality and ecosystem degradation are only moderately well quantified, and a number of cause-effect assumptions in this linkage need careful testing. Shifts in benthic community structure are clearly apparent across a range of enrichment regimes (see Section 8.1), but specific links between the abundance of many of the common invertebrate taxa and periphyton biomass have not been developed. Indeed, this may be difficult to do because of the degree of interaction between periphyton biomass and other variables. Figure 5: An aesthetically undesirable proliferation of filamentous green algae (mainly Oedogonium species) in a shallow gravel-bed river during summer low flows downstream of intensive agricultural development (Hakataramea River, North Otago). Enriched groundwater appeared to be entering the reach.

Figure 5: An aesthetically undesirable proliferation of filamentous green algae (mainly Oedogonium species) in a shallow gravel-bed river during summer low flows downstream of intensive agricultural development (Hakataramea River, North Otago). Enriched groundwater appeared to be entering the reach.

page-29-image

Clogging of intake structures for water abstraction is a common problem. This usually necessitates more regular, sometimes daily, maintenance of structures.

Table 3: Instream values that can be compromised and associated problems that may arise as a result of periphyton proliferations (based on MfE 1992 and Biggs, 2000).

page-30-image

Figure 6: Plume of filamentous green algae (Spirogyra) streaming from a groundwater upwelling at the side of a gravel-bed stream (Makara Stream, near Wellington).

4 Review of factors most commonly controlling periphyton growth and accumulation in streams

The following chapter reviews community processes and causal linkages as a basis for better understanding the potential effects of human activities on periphyton and criteria for the control of proliferations. Where possible, New Zealand examples are used to illustrate points.

4.1 The hierarchy of environmental controllers

The local factors controlling biomass and


Login