MTSRF
Project 3.7.1
Measuring the impact of poor water quality on inshore coral reefs
Project Leader: Dr Katharina Fabricius, AIMS
This MTSRF project has considerably furthered our understanding how poor water quality from river runoff affects a wide range of attributes of coral reef, seagrass and estuarine communities. Research quantifying the responses of corals and other reef-associated organisms to changing nutrients and sediments permitted the development of a set of indicators that is currently being tested within the Marine Monitoring Program for the Great Barrier Reef. Research results from this project have:
- been published in 28 peer-reviewed scientific papers and 10 student theses
- formed the basis for the Great Barrier Reef Marine Park Authority’s Water Quality Guidelines
- substantially contributed to and underpinned the Consensus Statement on Water Quality
- substantially contributed to GBRMPA’s first Outlook Report
- informed the Reef Rescue initiative as well as the Queensland Government’s Reef Regulations.
Perhaps most importantly, this MTSRF research project has contributed to a more informed and less confrontational public debate on this highly controversial issue, helping to build community consensus for better environmental management.
Using coral reef organisms as indicators of water quality and ecosystem condition
Project Leader: Dr Katharina Fabricius, AIMS
This MTSRF-funded project has confirmed that decreases in water quality cause profound multifaceted trophic shifts (from phototrophic to heterotrophic communities) and community shifts (from reef-building coral dominated communities to sites dominated by macroalgae and abiotic substrata) on the inshore Great Barrier Reef. Twenty-six environmental variables are strongly and specifically related to water quality conditions on the inshore Great Barrier Reef, and their potential usefulness as indicators of water quality for monitoring programs were investigated. Turbidity was by far the best predictor of biota and should be the fi rst priority for monitoring water quality on the inshore Great Barrier Reef. For example, colonies of massive Porites corals are darker in colour, and the density of macrobioeroders on living surfaces is higher, on reefs which experience higher turbidity and river influenced waters. Less diverse symbiont-bearing benthic foram communities are also observed on these reefs, and the ratio of phototrophic to heterotrophic foram taxa declines. In contrast, total macroalgal cover steeply increases from almost none in clear-water reefs to >50% cover in turbid water. Both total cover and the cover of specifi c genera of hard corals and octocorals declines as turbidity increases, and so does the taxonomic richness and juvenile densities and richness in both hard corals and octocorals. In cases where direct turbidity measurements are impractical or
too expensive, bioindicators may be a cost-effective alternative for monitoring changes in water quality. This research project has delivered a final list of 11 bioindicators useful for water quality monitoring on the Great Barrier Reef: Porites brightness, macro-bioeroder density in massive living Porites, Foram Index, macroalgal cover, Acropora cover, Acropora/Hard coral cover ratio, Turbinaria cover, juvenile hard coral density and richness, and juvenile soft coral density and richness. Additionally, Secchi depth readings taken every visit serve as a 12th indicator for water quality. A new multivariate approach to synthesising and integrating across multiple and unrelated indicators into one comprehensive and easy to use indicator system is now being tested. This new technique is derived from the indicator work conducted in this MTSRF project over the last four years, and if successful could become widely applicable for ecological indicator initiatives around the world.
Development of marine biofilms as indicators of changes in water quality
Project Leaders: Dr Katharina Fabricius & Dr Sven Uthicke, AIMS
As part of a larger project investigating the usefulness of a range of biological indicators of water quality, MTSRF-funded researchers have identified the organism groups in marine biofilms (bacterial biofilms on sediments, microphytobenthos layers on sediments, and foraminifera on sediment and other reef substrata) that consistently change along water quality gradients. The effects of light and nutrients on growth, mortality and photosynthesis were tested for several foraminiferan species both in laboratory experiments and in the field (through sampling under the Reef Rescue Marine Monitoring Program and experimental field transplants). Both foraminiferal growth rates and carbon/nitrogen ratios are reflective of local water quality conditions. Analyses of the influence of various stressors on foraminiferan distribution have improved our understanding of the thresholds of potential concern for pollutant exposure for individual organism groups and biofilm communities generally. Further experiments investigating interactions between water quality and climate change suggest that for at least one foram species, additive effects of the two stressors exist, and foram growth rates can be negatively affected by increased nutrient concentrations and increased temperature. Most species tested are clearly susceptible to bleaching at temperatures only slightly above current summer maxima, and thermal thresholds have been established for several foraminiferan species. The results of this project have been published in an easy-to-use web-based foraminiferan guide, a Standard Operational Procedure for foram sampling, a major step towards facilitating the use of foraminifera in water quality monitoring programs. In an immediate novel application of this new monitoring tool, these researchers have received MTSRF transition funding to investigate changes in water quality over the past 200 years by analysing changes in foraminiferan communities in dated sediment cores.
Publications
This report explores seagrass meadow dynamics in relation to proximity of catchments, nutrient quantity and quality in order to enhance the current understanding of anthropogenic impacts on the Great Barrier Reef World Heritage Area.
Report Series No. 12 - Nobes, K. and Uthicke, S. (2008) Benthic Foraminifera of the Great Barrier Reef: A guide to species potentially useful as Water Quality Indicators
Report by T. Cooper and K. Fabricius, Australian Institute of Marine Science for Project 3.7.1 Marine and estuarine indicators and thresholds of concern.
Report by K. Fabricius, Australian Institute of Marine Science. Coastal coral reefs are exposed to increasing loads of nutrients, sediments and other pollutants discharged from the land. Terrestrial runoff resulting in poor coastal water quality is therefore a growing concern. The objective of this study was to build a conceptual model to address the specific question, 'How are changes in river loads linked to changes in lagoonal water quality and biogeochemical processes, and do these changes alter the condition and ecological properties of coral reefs?'.
Unpublished report by C. Humphrey, S. C. King and D. Klumpp, Australian Institute of Marine Science, February 2007.
This report by Queensland Department of Primary Industries and Fisheries summarises baseline data and research results aimed at developing indicators for seagrass condition in response to contrasting sediment properties.
Report by James Cook University and Griffith University researchers on the assessment of techniques that can be employed to determine the ecosystem health of estuaries and coastal wetlands in Australia's tropical regions.