General

Chlorophyll a is a green pigment found in plants. It absorbs sunlight and converts it to sugar during photosynthesis. Chlorophyll a concentrations are an indicator of phytoplankton abundance and biomass in coastal and estuarine waters. They can be an effective measure of trophic status, are potential indicators of maximum photosynthetic rate and are a commonly used measure of water quality. High levels often indicate poor water quality and low levels often suggest good conditions. However, elevated chlorophyll a concentrations are not necessarily a bad thing. It is the long-term persistence of elevated levels that is a problem.

It is natural for chlorophyll a levels to fluctuate over time. Chlorophyll a concentrations are often higher after rainfall, particularly if the rain has flushed nutrients into the water. Higher chlorophyll levels are also common during the summer months when water temperatures and light levels are high because these conditions lead to greater phytoplankton numbers.

Tidal regime is an important control on algal biomass. Tidal mixing lowers chlorophyll a concentrations because the residence time of algae in the photic zone is reduced. Tidal mixing also causes fine sediment to resuspend, and the resulting turbidity reduces light available for photosynthesis.

Elevated concentrations of chlorophyll a can reflect an increase in nutrient loads and increasing trends can indicate eutrophication of aquatic ecosystems (Source: http://www.ozestuaries.org/indicators/In_chlorophyll_a_f.html)

Protocol

The standard method for analysing chlorophyll a in water samples is detailed in the Standard methods for the examination of water and wastewater – 20th Edition (APHA, 1998). Method number 10200H. Chlorophyll a is usually collected from water samples of a known volume that are filtered through fine mesh filter paper (0.45 micron) which is then analysed for chlorophyll a concentrations. It is also measured in-situ with special instruments. Regardless of how samples are collected, there are three standard methods for determining chlorophyll a. They are spectrophotometry, fluorometry and high performance liquid chromatography (HPLC). Spectrophotometry is the most commonly used method but the slower and more demanding HPLC method is able to differentiate between chlorophyll types, and accessory pigments.

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC/ARMCANZ, 2000) detail trigger values for Chlorophyll a. These can be found at http://www.deh.gov.au/water/quality/nwqms/pubs/volume2-8-2.pdf

Costs

Sydney Water - $25 per sample.

Case Studies

National Eutrophication Monitoring Program
http://www.rivers.gov.au/research/nemp/index.htm

Simple Estuarine Response Model - CSIRO
http://www.per.marine.csiro.au/serm/index.htm

People Contacts

Sydney Water sample receipt – Harold Jones 9334 0841.

Organisation Contacts

Various laboratories can undertake analysis for chlorophyll a. NATA certified laboratories should only be used to undertake chlorophyll a analysis.

Advanced References

ANZECC/ARMCANZ (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality. (www.ea.gov.au/water/quality/nwqms/#quality)

APHA (1998) American Public Health Association, American Water Works Association and Water Environment Federation Standard Methods for the Examination of Water and Wastewater – 20th Edition.

Wellman, S., Redden, A., Rissik, D., and Scanes, P. 2002. Phytoplankton production in near-pristine and urban-influenced coastal lagoons. Proceedings of the annual conference of the Australian Marine Sciences Association, 10-12 July 2002, Fremantle WA.

Ward, T., Butler, E. and Hill, B. 1998. Environmental Indicators for National State of the Environment Reporting, Estuaries and the Sea, Commonwealth of Australia, pp. 81. (www.ea.gov.au/soe/coasts/estuaries-ind.html)

Monbet, Y. 1992. Control of phytoplankton biomass in estuaries: A comparative analysis of microtidal and macrotidal estuaries. Estuaries 15(4), 563-571.

Cloern, J.E. 1987. Turbidity as a control on phytoplankton biomass and productivity in estuaries. Continental Shelf Research 7(11/12), 1367-1381.

Duarte, C.M. 1995. Submerged aquatic vegetation in relation to different nutrient regimes. Ophelia 41, 87-112.

Nielson, J. and P. Jernakoff, P. 1996. A review of the interaction of sediment and water quality with benthic communities. Port Phillip Bay Environmental Study. Technical Report No. 25, 1-130.

Hinga, K.R., Jeon, H. and Lewis, N.F. 1995. Marine eutrophication review I: Quantifying the effects of nitrogen enrichment on phytoplankton in coastal ecosystems. NOAA Coastal Ocean Office, Silver Spring, MD, 36p.

Nixon, S.W. 1992. Quantifying the relationship between nitrogen input and the productivity of marine ecosystems. Advanced Marine Technology Conference, No. 5, Japan, pp. 57-83.