Macroinvertebrate monitoring, analysis and synthesis for Coorong and Murray Mouth
Progress report and preliminary response to
“Condition of the RAMSAR site since listing”
for the Department of Environment, Water and Natural Resources
Sabine Dittmann, Ryan Baring & Tanith Ramsdale Flinders University, School of Biological Sciences
1. Background ... 3
2. Progress on Key Questions ... 3
2.2 Recovery ... 6
2.3 Annual Trends ... 7
2.4 Functions – Linkages to CPS ... 8
2.5 Conceptual Models ... 8
2.6 Ecosystem Condition ... 9
3. Preliminary response to Key Question “Change in Ecological Character since listing (1985)” ... 9
3.1 Macroinvertebrate communities at the time of listing (1981 – 1985) – species and distribution in the system ... 9
3.2 Current macroinvertebrate communities: 2013/14 - 2015 ... 10
3.3 Have macroinvertebrate communities changed since listing, and if so, how? ... 12
3.4 Were these change(s) beyond the bounds of normal seasonal (within years) or inter-annual (between years) and/or exceeded specified limits of environmentally acceptable change? ... 15
3.5 Were these changes adverse and, if so, were they human induced? ... 16
A. Appendix ... 17
A.1 Stocktake of Monitoring to Date ... 17
A.2 Recovery ... 28
A.3 Annual Trends ... 38
A.4 Conceptual Models ... 41
This progress report addresses the key questions for the analysis and synthesis of macroinvertebrate data based on response monitoring in the Murray Mouth and Coorong from 2010 to 2015. In
particular, this progress report includes a preliminary response to the final key question, “What is the Change in Ecological Character since listing (1985)”.
The information presented in this report is based on response monitoring undertaken since the restoration of flows in 2010, as well as comparisons to historical data for the system from monitoring since 2004 for The Living Murray” condition monitoring and studies by Geddes in the 1980s. In addition, information from similar systems in temperate Australia was considered for some questions as was biological information for key species known from the scientific literature.
2. Progress on Key Questions
The majority of the key questions outlined in Schedule 3 have been partially or completely addressed.
Analyses of datasets are complete and responses to most key questions have either been drafted or are in the process of being drafted for the final report. A summary of our progress towards completing the responses to each key question is provided in Table 1. Further detail regarding content that has been prepared for each key question is provided below and in the appendices for this report.
Throughout the following sections, references to figures and tables in the appendix precede with an A.
Layout and font sizes of some of the figures and tables in the appendix will be improved for the final report.
Table 1. Summary table of work completed, work in progress and work yet to start for each key question
Key Questions Components completed Components in progress
Components still to start Stocktake of
Monitoring to Date
Table of data collection periodicities over time
Percent contribution plots for 2010 – 2015 dataset. Includes comparisons for tidal position, years, regions, sites and low versus high taxonomic resolution.
Figures of total abundances,
abundances of various taxonomic groups, and species richness, diversity indices and index of occurrence.
Explanation of patterns in the dataset.
Various descriptive scenarios of alternate monitoring design that include less spatial, temporal and
taxonomic effort. (Near completion)
Overview with succinct recommendations.
4 Key Questions Components completed Components in
Components still to start Recovery Articulate hypotheses
regarding response outcomes.
Assess evidence to evaluate hypotheses.
Evaluate hypotheses based on available information using monitoring data and information from the literature.
2015 Monitoring survey report.
Annotated table detailing data currently available and future data requirements to address hypotheses.
Annual trends Define regions over years using
macroinvertebrate communities and salinity data (LinkTREE,
Explore community change over time using MDS trajectory plots
Identify species accounting for differences in communities using SIMPER
Relationship of macroinvertebrate communities to plankton and water quality.
Food web function with comparisons of
macroinvertebrate data and other levels of food web (e.g.
zooplankton, fish, birds).
Functions – Linkages to CPS
Comparison of macroinvertebrate abundances and biomass with the Paton Index of waterbird health
Review of data sets, reports and papers to evaluate energy transfer and food web flow on effects Conceptual
Detailed evaluation of species in the system, their environmental tolerances and species attributes
Comparison of historical and current communities
Species trends over time
Biological traits analysis
Update of existing conceptual models (currently working on)
Figure 18 South Lagoon integration
5 Key Questions Components completed Components in
Components still to start
DRAFT PREPARED Ecosystem
Information required to answer these
components comes from key questions that have already been completed (e.g.
Annual Trends, Recovery) or that are nearing completion (e.g. Conceptual Models).
Distribution of species categorised into response patterns
Analysis of changes in distributional ranges
Evaluation of potential indicator species
Evaluation of other possible
management tools for assessing system health
Site description and ranking of health Change in
ecological character since listing (1985)
Comparison of current and historical species distribution ranges
Comparisons of current and historical ecological character
Detailed species temporal
Comparison to other Ramsar listed estuaries
Quantified statement of whether site still meets Ramsar criteria
2.1 Stocktake of Monitoring to Date
An annotated table covering data periodicities was prepared for the response monitoring program between 2010 and 2015 (Table A1). Patterns of change in both intertidal and subtidal benthic macroinvertebrate abundances, percent contributions and species diversity indices (number of species, S; and species diversity, H’) were explored graphically and statistically (Figures A1 – A9). A four-factor nested PERMANOVA design (analysed using PRIMER + PERMANOVA version 7) was used to determine if there were significant differences in species abundances across time (years and months) and space (sampling regions and sites). Those investigations and analyses were explored to characterise and describe key patterns of the macrobenthos across time and space during the water release period, and a draft of this section has been completed. Key elements from that section are provided in Appendix A.1.
Scenarios on the effect of reducing sampling effort or taxonomic resolution were explored (Figure A10) and results are currently being prepared to discuss the findings of these investigations. Final recommendations for future design of monitoring studies in the Murray Mouth and Coorong Lagoons are also in preparation.
Hypotheses regarding the response of macroinvertebrates to flow restoration have been developed for both communities and individual species. At present, six hypotheses have been explored as follows:
It is hypothesised that continued environmental freshwater flows over the barrages into the Murray Mouth and Coorong Lagoons will result in changes in benthic macroinvertebrate communities, more specifically, that continued flow over the barrages will lead to;
1. Increases in benthic macroinvertebrate diversity and abundances;
2. Extended distribution ranges of benthic macroinvertebrates, with occurrences reaching further into the South Lagoon; and
3. Changes in the macroinvertebrate community structure, increasingly dominated by species larger in size and dwelling deeper in the sediment.
The mechanisms driving the hypothesised changes in macroinvertebrate communities have not been formally tested with manipulative experiments, but can be theoretically discussed based on patterns seen in our data and general scientific knowledge of estuarine and lagoon ecosystems. This includes consideration of species-specific traits affecting the ability to recolonise mudflats at locations where they had previously been lost during the Millennium Drought. Generally, it is expected that species- specific responses of macroinvertebrates to continued flow may be determined by;
4. Life-history (e.g. dispersal potential, reproduction, larval development) 5. Habitat suitability affecting recolonization (e.g. water and sediment quality) 6. Species interactions (e.g. predation, competition, bioturbation)
7 Hypotheses 1 and 3 were tested using multivariate PERMANOVA analyses using the same statistical design that was used to identify differences in abundance, diversity and community structure for the first key question, Stocktake of Monitoring to Date. Patterns in macroinvertebrate total abundance, species number and community structure have also been investigated graphically using bar graphs and Multidimensional Scaling (MDS) plots as appropriate (Figures A11 - A14).
Hypotheses 2 has been explored using graphical comparisons of distribution ranges of 5 key
species/taxa (Simplisetia aequisetis, Capitella spp., Amphipoda, Arthritica helmsi and Diptera larvae) in both the intertidal and subtidal benthos throughout the system across the monitoring period (2010 – 2015)(Figures A15 - A19) and for all taxa across the system using the index of species occurrence (Figure A20).
Hypotheses 4 – 5 have been investigated for 13 key taxa/species in the system using information on life-history traits, habitat requirements and species interactions for these taxa known from the literature. An evaluation of available data for individual species or taxa revealed that there are large gaps in our understanding of their biology, which makes a detailed assessment on recovery of those taxa very difficult. An annotated table of the known biology of these species/taxa has been prepared (Table A2).
A monitoring event was completed in February 2015 to determine if distributional changes for some taxa were still ‘playing out’. Eleven intertidal sites were selected throughout the system for this monitoring event. The findings of this single monitoring event have been presented in an interim report1 and incorporated into the analysis of long-term monitoring data to assess the benthic macroinvertebrate response to water flows in the Murray Mouth and Coorong Lagoons (upcoming final report).
The data included in this section were evaluated with patterns observed in the system described over several pages of text, and a draft of this section has been completed. Key elements from this section are provided in Appendix A.2.
2.3 Annual Trends
LinkTREE(+SIMPROF) was used to investigate community relationships to salinity over the
monitoring period (2010 – 2015) to define regions in the system based on biological assemblages and salinity rather than just geographical boundaries as done previously. This analysis revealed that there were changes in macroinvertebrate community structure both within years (seasonal changes) and across years as the system recovered from drought conditions in both the Murray Mouth and North Lagoon. However, south of Noonameena/Parnka Point, where conditions were consistently hyperhaline, there has been no change in overall community structure over the monitoring period (Figure A22, Table A3).
1Dittmann, S., Baring, R. & Ramsdale, T., 2015: Benthic Macroinvertebrate Response Monitoring in the Coorong and Murray Mouth, February 2015. Report for the Department of Environment, Water and Natural Resources, Adelaide.
8 MDS trajectory plots have been prepared for each region defined by the LinkTREE(+SIMPROF) analysis to investigate change in community structure over time (Figure A23). Those plots showed a clear pattern of change in community structure, especially in the Murray Mouth and Northern Coorong which could be related to changes in abundance of macroinvertebrate species over time as the system recovered.
The data included in these sub-sections were evaluated and the patterns described, and a draft text of this section has been completed. Key elements from this section are provided in Appendix A.3.
Work on two further subsections is yet to be started, as we are in the process of scheduling meetings with other service providers regarding the patterns and changes over time in other ecosystem
components, specifically fish, and how changes observed for macroinvertebrates have been reflected by other levels in the food web.
2.4 Functions – Linkages to CPS
Work on this section is scheduled for late July and August 2015 and is yet to be started. It will be informed by Biological Trait Analysis done for conceptual models (see 2.5).
2.5 Conceptual Models
Species inhabiting the system were identified and their distribution throughout the system (Table A4), environmental tolerances (Table A5) and attributes (Table A6) have been detailed in a series of annotated tables and discussed. Historical communities were detailed for the Coorong in an
annotated table and compared to current communities in the system (Table A7). Species trends over time were investigated using line graphs of average abundance for key species/taxa for each region across years (Figure A24).
Biological traits analysis was also completed on 17 species. Results from SIMPER analysis showed that the major contributing biological traits in the Murray Mouth diversified in every year through to 2015 (Table A8). Diversification in benthic reproductive strategies and the arrival of longer lived taxa started in the Murray Mouth during 2011/12 and 2012/13. During 2013/14 larger taxa, predatory feeding habits and deeper bioturbation started in the Murray Mouth. In 2015 biological traits such as filter feeding, benthic larvae and taxa with preference for euhaline (30-40 ppt) salinity conditions were more important in the Murray Mouth (Table A8, Figure A25).
In the North Lagoon the biological traits that changed from 2011/12 to 2012/13 were smaller taxa, pelagic planktonic larvae and preference for medium sized sand grain sizes (Table A8). There were no more changes to biological traits in subsequent years for the North Lagoon with mainly short lived, surficial sediment modification, and sediment surface and bentho-pelagic habits (Table 8, Figure A25). In 2010/11 and 2013/14 the biological traits in the North Lagoon were too inconsistent for reliable interpretation of the data (Table A8).
During 2010/11 and 2011/12 the South Lagoon had biological traits that mainly consisted of small- bodied, short lived, opportunistic, free living, pelagic or benthic larvae and only surficial sediment
9 modification (Table A8). In 2010/11, and 2012 to 2015 the biological traits in the South Lagoon were too inconsistent for reliable interpretation of the data (Table A8).
The current (2015) biological functioning of the macrobenthos varies between the Murray Mouth and the North Lagoon (Figure A25). In the Murray Mouth, there is deep bioturbation, benthic-pelagic coupling is increasing and the food web is diversifying compared to earlier years. For the North Lagoon, there is only surficial bioturbation, benthic-pelagic coupoing is only beginning and the food web is rather simple in comparison to the Murray Mouth (Figure A25).
The data included in these sub-sections were evaluated with the patterns described, and a draft text of this section has been completed. Key elements from this section are provided in Appendix 4.
Work on three further subsections; recruitment patterns, abundance and distribution of species over time and our conceptual understanding of benthic communities in the system was scheduled for late July 2015 and is in progress.
2.6 Ecosystem Condition
Work on this section is scheduled for late July and August 2015 and is yet to be started, although much of the background information needed to address this key question has already been compiled in other sections of the report.
3. Preliminary response to Key Question “Change in Ecological Character since listing (1985)”
What are the quantitative or qualitative changes in benthic macroinvertebrates?
3.1 Macroinvertebrate communities at the time of listing (1981 – 1985) – species and distribution in the system
Information on macroinvertebrates around the time of listing is only available from studies by Mike Geddes. These studies focussed on the Coorong, and data of macroinvertebrates at the times of listing are not available for the Murray Mouth.
Community types were qualitatively described for the Coorong Lagoons during a period of drought and then flow over the barrages between 1981 and 1985 (Geddes & Butler 1984; Geddes 1987).
These community types are summarised in Table 3.1 and A7 (see Conceptual Models; this report), and include; a freshwater community where estuarine polychaete worms and molluscs were either rare or absent; an estuarine community, when these species were present and even abundant in communities; a hypermarine community dominated by amphipods, Capitella sp. and larvae of salt- tolerant dipterans, and finally; a hypersaline community, where only isopods, ostracods and salt- tolerant dipteran larvae were present (Geddes & Butler 1984; Geddes 1987).
Only sites in the Coorong were sampled during the 1981 – 1985 monitoring period (Geddes & Butler 1984; Geddes 1987). In total, 14 sites were sampled by Geddes & Butler (1984) and Geddes (1987)
10 (Table 3.1) and some sites were the same or nearby to sites used in the current monitoring program.
The following summary of the description of macroinvertebrate communities has been adapted from qualitative descriptions in Geddes (1987) for communities at the end of the 1981 – 1985 monitoring period (ending approximately around 1984 – 1985); at the time when the site received Ramsar listing:
Conditions in the Coorong Lagoons had freshened following freshwater releases over the barrages after a 16 month period of no water release between 1981 and 1983. Estuarine conditions were recorded from just south of Pelican Point to Dodd Point (north of Noonameena), with hyperhaline conditions dominating south of the area around Noonameena (Table 3.1). Communities in the northern part of the North Lagoon, approximately between Pelican Point and Dodd Point were dominated by polychaete worms, Ficopomatus enigmaticus, Capitella capitata, Nephtys australiensis and Simplisetia aequisetis. During the same period, when conditions became estuarine, Boccardiella limnicola and Australonereis ehlersi were present (Table 3.1). Amphipods, the bivalves Arthritica helmsi and Spisula trigonella, and hydrobid snails were abundant, with Soletellina alba and Salinator fragilis present in lower abundances (Table 3.1). Decapods and insect larvae were also commonly found in samples (Table 3.1). Around Robs Point (south of Noonameena) to The Needles just north of Parnka Point, most polychaetes dropped out of communities as conditions were marine to
hyperhaline, with only F. enigmaticus, C. capitata and S. aequisetis remaining at times when salinities were lower (Table 3.1). The large bivalve, S. alba also dropped out of communities at this transition point (Table 3.1). When salinities at those Northern Coorong sites increased above 50 ppt, only C.
capitata, salt-tolerant dipteran larvae, hydrobiid snails and S. fragilis remained (Table 3.1). South of (and including) Parnka Point, conditions were hyperhaline and only salt-tolerant species of isopods, ostracods and insect larvae were able to tolerate the high salinities present (Table 3.1).
3.2 Current macroinvertebrate communities: 2013/14 - 2015
During the most recent monitoring years, salinity conditions in the Murray Mouth region, including all sites between Monument Road and Pelican Point, have typically been oligohaline in early summer and risen to polyhaline conditions by late summer, but the region could generally be considered to be estuarine overall (Table 3.1). Macroinvertebrate communities in this region have been dominated by the polychaete worm Simplisetia aequisetis, chironomid larvae and amphipods, with Arthritica helmsi becoming more common in samples in the most recent monitoring events (see Annual Trends A.3;
11 Table 3.1. Macroinvertebrate communities at sites throughout the Murray Mouth and Coorong at the time of Ramsar listing (1985; Geddes 1987) and
currently (2013/14 – 2015 monitoring events). Colours indicate approximate salinity conditions at the site (green: estuarine; blue: estuarine – marine; orange:
marine to hyperhaline; and red: hyperhaline to extreme hyperhaline) based on Whitefield et al. (2012). Salinity ranges for 1984-85 from Figure 1 in Geddes (1987). Salinity ranges for current conditions from LinkTREE analysis (see Figure A22; Appendix A.3; this report).
(ppt) Ficopomatus enigmaticus Capitella capitata Nephtys australiensis Boccardiella limnicola Australonereis ehlersi Simplisetia aequisetis Ampihpoda Isopod Ostracod Decapoda Insect Larvae (Diptera/Chironomidae) Arthritica helmsi Spisula trigonella Soletellina alba Hydrobiidae Salinator fragilis
(ppt) Ficopomatus enigmaticus Capitella capitata Nephtys australiensis Boccardiella limnicola Australonereis ehlersi Simplisetia aequisetis Ampihpoda Isopod Ostracod Decapoda Insect Larvae (Diptera/Chironomidae) Arthritica helmsi Spisula trigonella Soletellina alba Hydrobiidae Salinator fragilis
Monument Road - - - - - - - - - - - - - - - - - Monument Road 0.6 - 35 R X X P X P P X X X P P X X P P
Hunters Creek - - - - - - - - - - - - - - - - - Hunters Creek 3 - 30 X R R P X P P X X X P P R X P P
Mundoo Channel - - - - - - - - - - - - - - - - - Mundoo Channel 12 - 16.5 X X X P X P P X X X P P X X P R
Ewe Island - - - - - - - - - - - - - - - - - Ewe Island 3 - 40 X P P P R P P X X X P P R P P R
Pelican Point - - - - - - - - - - - - - - - - - Pelican Point 3 - 30 X R X P X P P X X X P P X X P R
Pelican Point Gate 10 - 30 P P* P* P P P* P X X P P P P P P P Pelican Point Gate - - - - - - - - - - - - - - - - -
Mark Point 10 - 30 P P P P P P P X X P P P P P P P Mark Point 9.5 - 40 X R X X X R P X X X P P X P X X
Mulbin-Yerrok - - - - - - - - - - - - - - - - - Mulbin-Yerrok 16 - 50 X P X X X P P X X X P P X X X X
Long Point 10 - 30 P P P P P P* P X X P P P P P P P Long Point 25 - 35 X P X X X P P X X X R P X X X X
Dodd Point 10 - 30 P P P P P P P X X P P P P P P P Dodd Point - - - - - - - - - - - - - - - - -
Noonameena 20 - 40 Noonameena 40 - 50+ X P X X R R P X X X P X X X X X
Robs Point 30 - 50 P P** X X X P P X X P P** P P X P** P** Robs Point - - - - - - - - - - - - - - - - -
The Needles 30 - 50 P P** X X X P P X X X P** P P X P P The Needles - - - - - - - - - - - - - - - - -
Parnka Point (NL) 50+ X X X X X X X P P X P X X X X X Parnka Point (NL) 50+ X P X X X X X R P X P X X X X X
Parnka Point (SL) - - - - - - - - - - - - - - - - - Parnka Point (SL) 50+ X X X X X X R X P X P X X X X X
Villa dei Yumpa 50+ X X X X X X X P P X P X X X X X Villa dei Yumpa 50+ X X X X X X R X R X P R X X X X
Stony Well Island 50+ X X X X X X X P P X P X X X X X Stony Well Island - - - - - - - - - - - - - - - - -
Woods Well 50+ X X X X X X X P P X P X X X X X Woods Well - - - - - - - - - - - - - - - - -
Jacks Point - - - - - - - - - - - - - - - - - Jacks Point 50+ X R X X X R R X X X P X X X X X
Policeman Point 50+ X X X X X X X P P X P X X X X X Policeman Point - - - - - - - - - - - - - - - - -
Loop Road 50+ X X X X X X X P P X P X X X X X Loop Road 50+ X R X X X R R X X X R X X X X X
Bul Bul Basin 50+ X X X X X X X P P X P X X X X X Bul Bul Basin - - - - - - - - - - - - - - - - -
Polychaeta Arthropoda Mollusca
Current (2013/14 - 15)
Polychaeta Arthropoda Mollusca
Time of Listing (1984 - 1985)
X Absent P Abundant
R Rare P* Abundant when estuarine but absent when fresh P Present P** Present when salinity higher (> 50 ppt)
12 Arthritica helmsi abundances started to recover in 2013 from very low abundances in the Murray Mouth region during the Millennium Drought (Figure A1). Capitella capitata was mostly confined to the North Lagoon since flows resumed in 2010, yet occurred at Ewe Island in 2015, possibly because of macroalgal mats seen at the site (Table 3.2). Amphipods were more abundant at sites in the Murray Mouth when conditions were freshest (Table 3.2) at the start of summer. Simplisetia aequisetis generally increased in abundance as conditions became more polyhaline in the Murray Mouth, towards late summer (Table 3.2). Many interactions could have resulted in the pattern of declines in amphipods abundances and increases in S. aequisetis abundances over summer months. Abiotic interactions (e.g. salinity increase over summer months), in combination with biotic interactions (such as competition or predation), are influencing the abundance and structure of benthic communities.
Sites in the northern North Lagoon (hereafter Northern Coorong), between Mark Point and Long Point, act as a highly dynamic transition zone from estuarine conditions in the Murray Mouth to hyperhaline conditions in the South Lagoon (Table 3.1). Salinity conditions range from mesohaline to euhaline, and communities were numerically dominated by Capitella capitata, amphipods and, also Arthritica helmsi during very recent sampling occasions (Tables 3.1, 3.2). The polychaete, Simplisetia aequisetis was also common in samples (Table 3.1), but did not reach the same high abundances in the Northern Coorong as were observed in the Murray Mouth (Table 3.2). Abundances of these species over the summer months were highly variable and showed no clear pattern for increase or decrease (Table 3.2), and likely reflect a response to the highly dynamic salinity conditions observed in this region.
Sites in the southern North Lagoon and South Lagoon (hereafter Southern Coorong), south of (and including) Noonameena were consistently hyperhaline, and macroinvertebrate communities in this region were generally depauperate (Table 3.1). Only larvae and pupae of the salt-tolerant dipteran families Chironomidae and Ephydridae were consistently present across sampling occasions and sites (Table 3.2). Ostracods, isopods and amphipods were sometimes present in samples and on rare occasions individuals of Simplisetia aequisetis, Arthritica helmsi and even Australonereis ehlersi were found (Table 3.2). The polychaete Capitella capitata was consistently present in samples from Noonameena, but only rarely observed further south (Table 3.1, 3.2).
3.3 Have macroinvertebrate communities changed since listing, and if so, how?
Comparisons between the two monitoring periods (1985 and current 2013-2015 surveys) are difficult to draw because of the purely qualitative nature of the data available from the 1980’s surveys (Geddes 1987). Overall, the taxa recorded in the system at the time of listing are generally still found in the Coorong and areas with similar salinity ranges are still represented by similar suites of
species/taxa as were observed at the time of listing. Between the times of 1985 and 2013-2015, two taxa, the polychaete Ficopomatus enigmaticus and decapod crustaceans, appear to be less widely distributed throughout the system during the more recent monitoring (Table 3.1). Sampling methods used for the more recent monitoring in 2013-2015 did not target these invertebrates well. For example, F. enigmaticus build reefs which were not included when collecting mudflat core samples.
13 Yet, observations were made during field trips and presence of live tubeworms recorded qualitatively, showing their presence in the North Lagoon to Noonameena. Decapods (represented in the 1980’s surveys by a single crab species) are highly mobile and not likely to be collected by coring into the muddy substrate. Yet we qualitatively recorded sightings of crabs during field work, and noted the presence of several species of decapod crabs, mostly in the Murray Mouth and northern North Lagoon.
Over time there appears to have been a shift in salinity conditions and macroinvertebrate distribution towards the Murray Mouth, with salinity conditions and fauna observed in the Northern Coorong at the time of listing now occurring in the Murray Mouth. Some of the large-bodied, deep burrowing species such as Australonereis ehlersi, Nephtys australiensis and Spisula trigonella are relatively rare in samples and only recorded at some sites, months or only in relatively low abundances (Table 3.1, 3.2). With only qualitative data available from the 1980’s surveys, it is not known if the relative abundances of these species has declined, remained stable or even increased. However, recolonisation of the sediment by those large-bodied, deep burrowing species is likely to be the beginning of the last successional steps in the recovery of this system following disturbance during the prolonged period of no freshwater flows during the Millennium Drought. Therefore, the larger- bodied, deep burrowing species may not become common in communities unless conditions continue to remain estuarine in the Murray Mouth into the future.
Many species previously recorded in the Northern Coorong region were not observed or rare during the most recent monitoring, particularly polychaete worms such as Nephtys australiensis, Boccardiella limnicola and Australonereis ehlersi, gastropod species and the large, deep dwelling bivalve species Spisula trigonella and Soletellina alba (Table 3.1). This may simply reflect the current position of the highly dynamic boundary between the Murray Mouth and Northern Coorong regions, with some of those species previously absent from sites once salinities increased to marine and hypermarine levels (Table 3.1). Salinity conditions in the southern part of the North Lagoon at Noonameena are similar to those observed at Robs Point and The Needles in the past, but none of the mollusc species
previously observed in this region have been recorded during recent monitoring (Table 3.1). Across the Northern Lagoon, most mollusc species recorded at the time of listing have not been recorded during recent monitoring, even though they can tolerate the higher salinities that are currently observed in the region (Table 3.1).
There has been no apparent shift in the boundary of the Southern Coorong hyperhaline region (Table 3.1). In the hyperhaline Southern Coorong region, species compositions are largely unchanged, with communities still dominated by salt-tolerant dipteran larvae, isopods and ostracods, with some amphipods also found during recent monitoring (Table 3.1). Capitella capitata were sometimes observed in the Southern Coorong, particularly during December at Parnka Point, but populations of this species do not appear to persist (Table 3.2).
14 Table 3.2. Detailed macroinvertebrate species abundances (numbers are average individuals/m2 for each site/sampling occasion) at each site sampled and each sampling occasion for the monitoring period 2013/14 – 2015. Zero abundances are highlighted by dark hatching. Groups identify
community types from the LinkTREE(+SIMPER) analysis (see Annual Trends; this report) with their associated salinity ranges also listed (Salinity (ppt)). Colours have been used to highlight the different groups and correspond to those used in Figure A22 (see Appendix A.3; this report).
Region Site Year Month Group Salinity
(ppt) Ficopomatus enigmaticus Capitella capitata Nephtys australiensis Boccordiella limincola Australonereis ehlersi Simplisetia aequisetis Phylodoce novaehollandia Amphipoda Isopoda Ostrocoda Decapoda Chironomid (Larvae + pupae) Ephydridae pupae Arthritica helmsi Spisula trigonella Soletellina alba Hydrobiidae Salinator fragilis
2013/14 Dec 5 0.6 - 1 0 0 0 2172 0 7753 38286 0 0 2268 0 0 0 0 72 48
2013/14 Feb 14 16 - 24 0 0 0 672 0 2340 276 0 0 1224 0 0 0 0 1272 72
2013/14 Mar 13 30 - 35 12 0 0 156 0 2088 300 0 0 144 0 0 0 0 1068 60
2015 Feb 16 15 - 16.5 0 0 0 2964 0 13226 20763 0 0 2364 0 1980 0 0 1128 24
2013/14 Dec 7 3 - 6 0 0 0 1584 0 5317 88970 0 0 3865 0 396 0 0 360 12
2013/14 Feb 12 25 - 30 0 0 12 1464 0 4213 324 0 0 192 0 660 96 0 12 24
2013/14 Mar 12 25 - 30 0 12 0 1032 0 4369 3709 0 0 540 0 4333 0 0 288 48
2015 Feb 16 15 - 16.5 0 0 0 1284 0 7369 9974 0 0 852 0 15242 0 0 168 24
2013/14 Dec 15 12 - 15 0 0 0 1308 0 8953 54825 0 0 9650 0 252 0 0 552 0
2015 Feb 16 15 - 16.5 0 0 0 3589 0 14354 51764 0 0 2424 0 46135 0 0 2304 120
2013/14 Dec 7 3 - 6 0 0 180 60 36 1956 103361 0 0 6937 0 216 0 96 192 0
2013/14 Feb 13 30 - 35 0 36 48 108 12 5533 180 0 0 156 0 1224 0 60 120 24
2013/14 Mar 10 35 - 40 0 156 0 12 0 4705 264 0 0 48 24 444 12 0 24 0
2015 Feb 16 15 - 16.5 0 5893 0 276 36 16503 29081 0 0 360 0 36690 0 60 1668 36
2013/14 Dec 7 3 - 6 0 0 0 876 0 9962 44575 0 0 492 12 588 0 0 168 0
2013/14 Feb 12 25 - 30 0 12 0 48 0 1668 24 0 0 24 12 804 0 0 12 12
2013/14 Mar 12 25 - 30 0 0 0 48 0 2352 168 0 0 960 0 168 0 0 60 24
2015 Feb 16 15 - 16.5 0 0 0 888 0 11066 1824 0 0 132 0 26752 0 0 396 0
2013/14 Dec 11 9.5 - 10.5 0 12 0 0 0 48 96 0 0 0 996 144 0 0 0 0
2013/14 Feb 12 25 - 30 0 0 0 0 0 0 0 0 0 0 120 144 0 0 0 0
2013/14 Mar 10 35 - 40 0 0 0 0 0 0 24 0 0 0 168 0 0 0 0 0
2013/14 Dec 14 16 - 24 0 44011 0 0 0 8413 115999 0 0 396 0 3325 0 60 0 0
2015 Feb 2 40 - 50 0 29777 0 0 0 9866 7609 0 0 0 0 10706 0 0 0 0
2013/14 Dec 12 25 - 30 0 29849 0 0 0 5365 6529 0 0 12 0 396 0 0 0 0
2013/14 Feb 13 30 - 35 0 35454 0 0 0 3949 120 0 0 0 0 564 0 0 0 0
2013/14 Mar 13 30 - 35 0 7777 0 0 0 2016 216 0 0 0 0 48 0 0 0 0
2013/14 Dec 1 > 50 0 38634 0 0 156 0 228 0 0 1548 1236 0 0 0 0 0
2013/14 Feb 1 > 50 0 132 0 0 0 0 0 0 0 0 384 0 0 0 0 0
2013/14 Mar 2 40 - 50 0 1908 0 0 0 0 0 0 0 12 984 0 0 0 0 0
2015 Feb 1 > 50 0 19575 0 0 0 672 0 0 0 108 0 0 0 0 0 0
2013/14 Dec 1 > 50 0 4153 0 0 0 0 0 12 1524 6841 0 0 0 0 0 0
2015 Feb 1 > 50 0 0 0 0 0 0 0 0 0 780 0 0 0 0 0 0
2013/14 Dec 1 > 50 0 0 0 0 0 0 0 0 52484 432 12 0 0 0 0 0
2013/14 Feb 1 > 50 0 0 0 0 0 0 0 0 16983 48 0 0 0 0 0 0
2013/14 Mar 1 > 50 0 0 0 0 0 0 12 0 12338 72 48 0 0 0 0 0
2013/14 Dec 1 > 50 0 0 0 0 0 0 24 0 192 240 300 24 0 0 0 0
2013/14 Feb 1 > 50 0 0 0 0 0 0 0 0 0 72 0 0 0 0 0 0
2013/14 Mar 1 > 50 0 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0
2015 Feb 1 > 50 0 0 0 0 0 0 0 0 0 36 0 0 0 0 0 0
2013/14 Dec 1 > 50 0 12 0 0 0 24 60 0 0 60 12 0 0 0 0 0
2015 Feb 1 > 50 0 0 0 0 0 0 12 0 0 24 0 0 0 0 0 0
2013/14 Dec 1 > 50 0 12 0 0 0 0 24 0 0 24 0 0 0 0 0 0
2015 Feb 1 > 50 0 0 0 0 0 12 0 0 0 0 0 0 0 0 0 0
Polychaeta Arthropoda Mollusca
Ave. Macroinvertebrate abundance (ind/m2)
15 Overall, it seems that many of the larger-bodied, deeper dwelling species of polychaetes and bivalves are still recovering with regard to both distributional ranges and population abundances in the system following the prolonged Millennium Drought of 2005 – 2010. Whether these species continue to recover and recolonise sites where they were previously distributed at the time of Ramsar listing will depend on future environmental conditions and freshwater flows into the system to maintain estuarine conditions.
3.4 Were these change(s) beyond the bounds of normal seasonal (within years) or inter-annual (between years) and/or exceeded specified limits of environmentally acceptable change?
The most notable change in the system since listing has been the reduction in occurrence and spatial distribution of large-bodied, deep dwelling species such as Australonereis ehlersi, Nephtys
australiensis, Soletellina alba and Spisula trigonella, especially from the Northern Coorong. Without a detailed understanding of the nature of the Coorong prior to installation of barrages and flow
regulations across the whole Murray-Darling system, or even quantitative data from the time of listing, it is difficult to say whether these changes are beyond the bounds of natural seasonal and inter- annual variation for these species. No historic data exist for seasonal patterns.
Unfortunately there is no quantitative or qualitative evidence indicating what macroinvertebrate communities were like prior to flow regulations in the Murray Mouth and Coorong Lagoons. Anecdotal evidence from the Ngarrindjeri people tells us that the system once received freshwater inputs from both the River Murray in the north and the South East in the south, and that salinity changed
seasonally from freshwater to marine conditions as freshwater flows varied across the year (Phillips &
Muller 2006). After the installation of flow regulators (barrages and weirs) into the Murray Darling system during the 1940s, salinities rose noticeably in the 1970s and the ecological condition of the system began to decline (Phillips & Muller 2006). Freshwater flows that previously flushed the system from Salt Creek in the South Lagoon ceased (Phillips & Muller 2006), and it is likely that salinity increases in the Southern Coorong led to a decline in macroinvertebrate communities as conditions became increasingly hyperhaline. Thus it is highly unlikely that the macroinvertebrate community currently observed in the Southern Coorong, or that which was observed at the time of Ramsar listing, is natural to the region. It is more likely that the community currently observed in the Murray Mouth and previously observed in the Northern Coorong in the 1980s once extended across the whole Murray Mouth and Coorong.
Early macroinvertebrate surveys were qualitative (Geddes & Butler 1984; Geddes 1987), and there is no information on the levels of natural variation in species or communities at the time of Ramsar listing. Anecdotal evidence suggests that the system had in fact been declining in health for 30 years prior to listing, and that declines observed since listing were the result of changes that had been occurring since flow regulation began (Phillips & Muller 2006). Since flow regulations began, the system has been subject to periods of no-flow (drought), small flows and some large flows over the barrages, with fewer periods of continuous flows of different durations. It is likely that
macroinvertebrate communities have been responding to changing salinity conditions throughout the