Gladstone Healthy Harbour Partnership Pilot Report Card. ISP011: seagrass final report

Executive Summary: The Seagrass Ecology Group within the Centre for Tropical Water and Aquatic Ecosystem Research at James Cook University (TropWATER) have developed a pilot approach for reporting on the condition of seagrasses in the Gladstone Harbour region for incorporation into the Gladstone Healthy Harbours Partnership (GHHP) 2014 pilot report card. Annual long term monitoring data collected at 15 representative seagrass meadows since 2002 were used to assess the status of three seagrass indicators (average above-ground biomass, total meadow area and species composition) relative to baseline conditions at each meadow.We assessed various methods for setting baseline conditions including a running long term average; a ten year fixed average; and a five year fixed average applied across two different portions of the monitoring history. The ten year fixed average (calculated over the period from 2002 – 2012) was considered the most appropriate baseline for which to compare annual indicator values because it incorporated the greatest range of climate conditions known to influence seagrasses in the region. Threshold levels determining the condition of indicators relative to the baseline were selected based on the historical variability within the monitoring meadows and expert knowledge of the different meadow types and assemblages in the region. We tested several ranges of threshold values to determine which ranges best fit the historical data, i.e. which ranges resulted in a grade that reflected our understanding of the condition of seagrasses over the course of the monitoring program. A combination of threshold ranges were used, recognising that some seagrass meadows are historically more stable and others are expected to fluctuate substantially from year to year. These differences reflect the difference in species assemblages and growth characteristics at various monitoring meadows as well as regional difference between meadows growing in marginal inner harbour versus more favourable outer harbour conditions. The pilot reporting framework assesses annual levels for each seagrass indicator against baseline conditions to determine a grade from A to E, where A indicates a condition of 'very good' and E indicates a condition of 'very poor'. The lowest of the three seagrass indicator grades dictates the overall grade for each monitoring meadow. The harbour has been divided up into several zones as part of the GHHP reporting process. The average of the individual meadow grades within each of these zones dictates the overall grade for each zone. The report is separated into two parts. Part 1 presents the results of the 'pilot' report card approach applied to the results of the most recent annual survey conducted in November 2013 (in the GHHP 2014 reporting year). Part 2 is an accompanying technical report detailing the methods for data collection, justification for the pilot reporting framework and a detailed interpretation of monitoring results. Key findings: Seagrasses in the Gladstone and Port Curtis region underwent significant declines following flooding and major rain and storm activity in 2010, similar to many areas of seagrass along the Queensland east coast. Annual monitoring has shown that during 2012 some recovery occurred at many meadows, but high rainfall and the biggest flow event for the Calliope River in over a decade in early 2013 saw a reversal of much of that recovery. Most monitoring meadows were assessed as being in a poor (D) or very poor (E) condition in November 2013, including the majority of meadows in The Narrows, Western Basin, Inner Harbour, South Trees Inlet (lower) and Rodds Bay Zones. In the Mid Harbour Zone, the large Pelican Banks and Quoin Island monitoring meadows were in a moderate (C) condition but above-ground seagrass biomass and/or total meadow area remained well below the baseline. Several consecutive years of decline have likely left seagrasses with a reduced resilience to further impacts and it may take some time for meadows to reach pre-flood (2009) levels. The generally poor condition of seagrasses in Gladstone is reflected in other monitoring locations on the east coast of Queensland. This is in contrast to many of the seagrass areas on Northern Cape York and the Gulf of Carpentaria which were in good condition and not impacted by the severe flooding that occurred on the east coast in recent years.This is the first year of applying and testing the seagrass report card framework and there is scope for future modifications as the program is rolled out and implemented in 2015. The pilot approach relied heavily on expert opinion for setting baseline conditions and thresholds to determine grades. For future reporting we are exploring statistical approaches to potentially enhance the strength of the reporting framework.