Title

Research for the management of seagrass resources in the Dugong Protection Areas of the Great Barrier Reef region

Objectives

1. To conduct one summer and one winter baseline survey of each DPA (where a baseline does not already exist).
2. To re-survey the seagrass resources (inshore and deep-water) on a fine-scale each summer within each of the Dugong Protection Areas of the Great Barrier Reef (Oct–Nov 98, Oct–Nov 99, Oct–Nov 2000, Oct–Nov 2001).
3. To produce each year a detailed (fine-scale) Geographic Information System on seagrass habitats within each of the DPAs.
4. To monitor long term trends in seagrass parameters (abundance, productivity, species composition, etc.) at two localities (possibly Mission Bay – Cairns and Missionary/ Shepherd Bays – Hinchinbrook) by sampling every two months for three to four years to identify changes and potential impacts which may cause loss of seagrass habitats and consequently dugong populations.
5. To broad-scale map non-DPA coastal areas of seagrass that are potential food for dugongs and to confirm estimated areas of seagrass species used by dugongs identified in 1980–1987 surveys (Cooktown – Cardwell, Bowling Green Bay – Rockhampton, Rockhampton – Bundaberg).
6. To identify areas of seagrass with a distribution and species composition ideal for dugong feeding areas and to estimate long-term trends.
7. To provide information needed to further improve understanding of the relationship between dugong feeding behaviour and the location and species characteristics of seagrasses.
8. Complete a cartographic model which identifies seagrass habitats using a set of replicable physical, environmental and resource use parameters, to assist in regional scale assessment of seagrass and dugong distributions.
9. To provide a strategic plan for seagrass management in the southern Great Barrier Reef.

Relevance

Seagrasses are essential food for dugongs and there is relatively little information on the health and distribution of seagrasses within the Great Barrier Reef Marine Park and World Heritage Area. Information that is available is broad-scale and over 10 years old.

Dugong populations in the Great Barrier Reef Marine Park south of Cooktown have declined dramatically since 1987. In November 1996, at a meeting of the Great Barrier Reef Ministerial Council, it was agreed that emergency action was required to save dugongs in the Great Barrier Reef World Heritage Area. The Ministerial Council acknowledged that one of the reasons for the decline in dugong numbers may be habitat loss.

Broad-scale surveys by the Queensland Department of Primary Industries & Fisheries (QDPI&F) of separate regions from 1984 to 1989 indicated where seagrasses occurred in estuaries, shallow coastal bays and inlets, on some fringing reefs, barrier reef platforms and limited sites in deep water. Coastal waters were broadly mapped for all of Queensland, but surveys of deeper water

(>15 m), inter-reef, inshore-reef and barrier-reef platform areas have only recently begun. Seagrasses have been found to depths of 58 metres in the Cairns and Far Northern Sections.

Despite being 10 years old these maps are being used to support a case for excluding some types of activities, particularly net fishing, from areas where seagrasses were found. Research at Shoalwater Bay and the CRC-funded deep water surveys together with work on dugongs suggest the relationship between dugong feeding behaviour and their seagrass food is complex. The species of seagrass, its location and the tidal range of the area, the depth of the seagrass and the seasonality of the seagrass growth rate are all important factors. For example, a seagrass bed at 10 metres may be a food source for an adult dugong but not suitable for a neonatal calf. A relatively small but suitable area of seasonal Halophila may be far more important in the dugong life cycle than anticipated by aerial surveys of animal distribution. While the establishment of Dugong Protected Areas is an important step it is also important to continue research on the dugong’s food source. It is appropriate to have an up-to-date picture of the seagrass resource on which to base management decisions and it is important to have some knowledge of the options available to dugongs in the event of major changes in seagrass distribution or loss.

Natural cyclone and flood events in some locations have caused loss of seagrasses. Agricultural land-use practices may exacerbate the effects of these natural events or reduce the resilience and recovery of seagrasses from natural impacts. The most immediate threats from urban and agricultural run-off, or coastal and Barrier Reef development appear in southern, populated regions. Localities which have shelter and water conditions ideal for productive seagrass habitat are often sites for port development, and/or are at the downstream end of heavily disturbed catchments.

There is no information on productivity for most seagrass species, areas and habitat types. This is a major gap in the knowledge base required for effective management. Dugongs and those fish, turtles and prawns dependent on seagrasses for food rely on both available area of seagrass and the productivity (plant growth rate) as these determine the total available food and nutrient source. Changing conditions such as poorer light penetration could reduce seagrass productivity (leaf and root production and/or nutritional value) and increase the area of seagrass required to support a dugong. Seagrass area may not be effected by some downstream effects but productivity may be. Area alone is not necessarily the best measure of the ability of an area to support the food requirement of dugongs and fish/prawn populations.

Natural seasonal variation in biomass has been documented and more recent detailed surveys have indicated some large long-term changes in seagrass areas at regional scales, although natural year-to-year change in Queensland seagrasses remains little studied and the causes, scale and ecological consequences of long-term changes are poorly understood. Seagrass monitoring programs need long-term support. Large seasonal variations make it hard to detect loss over a short period of time. Trend analysis over several years will provide an early warning of potential problems.

Feasibility and other closely related projects

Detailed (fine-scale) surveys have been successfully conducted by the Seagrass Ecology Group from the Northern Fisheries Centre (QDPI&F) at several localities. Methodologies are established and have been reviewed by both the scientific and resource management communities.

• The objective to monitoring long term trends in seagrass parameters (abundance, productivity, species composition, etc.) overlaps with CRC Reef Research Task 1.4.2, and vessel charter and equipment costs are predominantly covered by current funding from CRC Reef Research Centre and have been taken into account in this proposal.
• CRC Reef Research Task 1.4.6 currently provides part funding for a Research Scientist and Biologist to obtain a detailed baseline measure of coastal, deepwater and reef platform seagrass resources in the Great Barrier Reef province. These staff could assist with the supervision and field work for some sections of the current proposal and this has been taken into account in the budget.
• Seagrass surveys of deep-water (>15 m) resources are currently conducted under CRC Reef Research Task 1.4.6. This current proposal and CRC Task 1.4.6 compliment each other in providing a complete coverage of the southern Great Barrier Reef regions (Cooktown – Capricorn Bunker Group).

Methodology

1. The sampling design for the baseline and monitoring surveys of the DPAs will be similar to the fine-scale surveys conducted recently by QDPI in localities such as Shoalwater Bay and Dunk Island – Cape Cleveland. Sampling intensity will be at a level adequate for mapping boundaries of seagrass communities.
2. The sampling design for the broad-scale surveys of seagrass resources between Cooktown and Hervey Bay (excluding DPAs) would be similar to previous surveys conducted by QDPI. Sampling intensity would be set at a level adequate for identifying the boundaries of seagrass communities. A combination of dive sampling and video camera techniques would be used.
3. Methodologies for measuring the productivity of deep-water plants are similar to shallow/near-shore plants, however they are currently being modified so as not to compromise safe diving practices.
4. All data would be entered on a Geographic Information System (GIS) as a tool to overlay dugong distribution and movement. The maps of habitat types will provide a tool for interpretation and assessment of possible impacts.

Cost

Salaries of temporary biologists and technicians are estimated at $212 000 per year in 1998–99, increasing at 5% annually. Each survey requires a minimum of five to six persons (suitably experienced and qualified occupational divers) to conduct fieldwork. Operating costs include vessel charter, travelling expenses, data analysis and preparation. Each survey requires one support vessel and two small survey vessels. Capital costs include the purchase of two differential Global Positioning System rovers ($20 000) and a GIS work station ($7500) in 1998–99.

Time required

This project is to conduct winter and summer baseline surveys of seagrass distribution and abundance within the nine proposed Dugong Protection Areas of the Great Barrier Reef Marine Park, and re-map seagrass meadows in each DPA for three years to assess any changes or impacts which may effect dugong populations. The project would be initiated in Summer 1998. Interim reports and GIS maps will be available approximately four months after each baseline or monitoring survey, so that any changes or major losses can be identified and appropriate management strategies implemented. The project will conclude in Winter 2002, and a major report will be produced summarising results of the monitoring program and recommendations for continued monitoring and management.

Seagrass productivity of key species will be monitored in selected areas (possibly Mission Bay – Cairns and Missionary/Shepherd Bays – Hinchinbrook), six times a year over a period of two to three years. The project would be initiated in Summer 1998. A summary of results will be available each year in the form of interim reports, so that any finding of importance to management can be identified and appropriate management strategies implemented. The project will conclude late 2001, after which a major report will be produced summarising results of the study and recommendations for further research and management.

The broad-scale mapping of seagrass resources between Cooktown and Bundaberg (excl. DPAs) could commence in October 1998 and be completed in 2000. The three sections would be Cooktown to Cardwell in 1998; Bowling Green Bay to Rockhampton in 1999 and Rockhampton to Bundaberg in 2000. Information would be available in GIS form early in the year following each survey.