Journal of the Royal Society of Western Australia, 94:171-179, 2011 Potential effects of Lyngbya majuscula blooms on benthic invertebrate diversity and shorebird foraging ecology at Roebuck Bay, Western Australia: preliminary results S M EstrellaA W Storey1, G Pearson2 & T Piersma3-4 1 School of Animal Biology (M-092), The University of Western Australia, 35 Stirling Hwy, Crawley, W.A. 6009, Australia. El [email protected] 2 Bennelongia Pty Ltd. 5 Bishop Street, Jolimont, W.A. 6014, Australia. 3 Animal Ecology Group, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, P.O. Box 45, 9750 AA Haren, The Netherlands. 4Department of Marine Ecology and Evolution, Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59,1790 AB Den Burg, Texel, The Netherlands. Manuscript received November 2010; accepted April 2011 Abstract Nutrient enrichment can significantly alter biodiversity, producing shifts in assemblages of primary producers and favouring, for example, cyanobacterium blooms. These variations in the assemblage of primary producers consequently affect the primary consumers that depend on them. However, the consequences of these blooms for higher trophic levels are still unclear. Roebuck Bay, in the west Kimberley region is one of the main non-breeding areas for migratory shorebirds in Australia. The bay is characterised by an extremely high diversity and biomass of benthic invertebrates, which places this tropical intertidal area among the richest mudflats in the world, and it is likely that this rich benthic fauna supports the shorebird populations. Recent studies in Roebuck Bay have detected nutrient enrichment, with increasing frequency of cyanobacteria blooms. Here we present the preliminary results of the potential effects that Lyngbya majuscula (cyanobacterium) blooms have on the benthic invertebrate diversity and shorebird foraging ecology at Roebuck Bay. A site where Lyngbya majuscula was present showed a significant diminution in the diversity of benthic invertebrates relative to areas without a bloom. Also, although there was no apparent Lyngbya - i n d u ce d change in the main prey of Bar-tailed Godwits Limosa lapponica, there was a change in the foraging behaviour of godwits in the area affected by Lyngbya, which appears to relate to a shift in diet. Nevertheless, although we found a correlation between Lyngbya presence and shifts in invertebrate assemblages, further work is required to confirm our findings. Keywords: Lyngbya majuscula blooms, benthic invertebrate, shorebirds. Roebuck Bay, Kimberley Introduction throughout the world (Vitousek et al. 1997; Edgar et al. 2000). A major challenge in ecology and conservation Anthropogenic nutrient enrichment of wetlands has research is to improve our understanding of ecosystem become a premier issue for both scientists and managers. diversity and function to develop proper protection, Studies of nutrients loads on aquatic systems have monitoring and management programs that assure their determined that nutrient enrichment can significantly existence for future generations. Coastal ecosystems are alter biodiversity, producing for example shifts in the heterogeneous, often being characterised by high levels assemblages of primary producers and favouring of production (Borges et al. 2006) and an immense phytoplankton, cyanobacterium or macro-algal blooms diversity of ecological processes (Constanza et al. 1993). that are related to episodes of anoxia and hypoxia However, coastal habitats are also subjected to high (Cloern 2001). These variations in the assemblage of anthropogenic pressure, and as a result they represent primary producers consequently affect the primary the most endangered ecosystems in the world (Duarte consumers that depend on them, often causing them to 2007). More than one third of the human population lives disappear (Valiella ef al. 1997; Tewfik et al. 2005). on the coast and consequently between 30% and 50% of However, the consequences of such blooms of primary the world's principal coastal areas have been degraded producers for higher trophic levels are still unclear. in the last three decades (Duarte 2007). Determination of the effects that human activities have on these Worldwide there are less than twenty regions where ecosystems is of primary importance since large mudflats rich in shorebirds are found at low tide overharvesting of marine organisms, land reclamation and only two are located in tropical regions. Roebuck and more recently, nutrient loading and climate change Bay being one of them. Roebuck Bay, located in North- are pervasively changing coastal wetland ecosystems Western Australia is one of the main non-breeding areas for migratory shorebirds of the East Asia-Australasian © Royal Society of Western Australia 2011 Flyway (Bamford et al. 2008). The importance of Roebuck 171 Journal of the Royal Society of Western Australia, 94(2), June 2011 Bay appears to relate to the elevated diversity and enrichment of the foodweb (A.W. Storey, UWA, unpub. biomass of benthic invertebrates (the primary food source data 2006). A preliminary assessment of the nutrient of shorebirds), which places this tropical intertidal area loads in sediments adjacent to Broome's Town Beach among the richest mudflats in the world (Rogers et al. indicate elevated levels of P and N (Pearson 2008) and 2003). The number of shorebirds using Roebuck Bay may blooms of cyanobacterium (blue-green algae) Lyngbya exceed 125,000 in the non-breeding season (Rogers et al. majuscula first appeared during the 2005 wet season, and 2011), making it one of the most important two shorebird have increased in extent each wet season since then (de sites in Australia (Rogers et al. 2003; Rogers et al. 2011). Goeij et al. 2008; Pearson 2008). However, 20% of shorebird species that regularly migrate Here we present the preliminary results of ongoing along the East Asian-Australasian Flyway have been research looking at the effects that Lyngbya majuscula officially classified as globally threatened, possibly due blooms have on the benthic invertebrate diversity and to land modification or habitat degradation along the shorebird foraging ecology in Roebuck Bay. flyway (Rogers et al. 2010). Therefore there is an urgent Some described effects of Lyngbya majuscula and other need to monitor and conserve the remaining important cyanobacterium on marine organisms have been sites in the flyway. Roebuck Bay was designated as a attributed to the changes produce in the physicochemical Wetland of International Importance in 1990 under the and biological conditions of the habitat (e.g. anoxia, Ramsar Convention (1971), has been recently proposed covering and smothering of seagrass meadows - e.g. as a Marine Park, and currently ranks in the top 8 Watkinson et al. 2005). It is expected then that Lyngbya migratory shorebird non-breeding sites in the world blooms affect the benthic invertebrate abundance (Garda (Rogers et al. 2003). It is, therefore, a highly significant and Johnstone 2006) and diversity in affected areas of bird habitat worthy of preservation at a national and Roebuck Bay. Consequently Lyngbya blooms could international level. reduce shorebirds' prey availability. This change of Roebuck Bay is adjacent to the tourist town of Broome habitat conditions may have long term effects at a (15,857 inhabitants - data for 2009, Australian Bureau of population level, since the loss or degradation of Statistics. Population could double during the tourist migratory shorebirds' habitats anywhere along their season), and recent studies indicate a developing issue flyways is capable of precipitating a decline in their with respect to nutrient contamination. A study on populations (Galbraith et al. 2002; Thomas et al. 2006). regional groundwater has shown elevated nutrient levels in water originating from the area of Broome and moving into the bay (Vogwill 2003). Stable isotope studies have Methods detected elevated 8l5N signature in phytoplankton and filamentous algal from the bay, indicative of nutrient Study sites Roebuck Bay has a tropical climate, with a warm-dry season (May-November), followed by a hot-wet season (December-April). In other areas of Australia, such as Moreton Bay, nutrient inputs together with high temperatures, light conditions and iron availability drive Lyngbya blooms (Albert et al. 2005; Ahern et al. 2008; Johnstone et al. 2010). Lyngbya blooms occur in the wet season each year in the bay (G. Pearson and A.W. Storey personal observations), which appears to indicate that nutrient inputs, result of rainfall run-off that occurs in the wet season, drive Lyngbya blooms together with high water temperatures. In line with this, two sampling programs were carried out, one at the end of the dry season (November 2009) before any bloom was evident, and another mid wet season (February 2010) when Lyngbya majuscula was present in the bay. The study was carried out at three locations. Sites were selected in intertidal areas to characterize: (1) an area potentially affected by wastewater treatment plant/ urban activities, presenting a high density of Lyngbya throughout the wet season (Town Beach, TB), (2) an area located in the mouth of a tidal creek potentially affected by wet season runoff from pastoral land (One Tree, OT), and (3) an area situated in the proximity of an extensive mangrove area and away from obvious nutrient sources (south of Crab Creek, SCC) (Fig. 1). Town Beach site is characterized by sandy sediments (Pepping et al. 1999; Piersma et al. 2006), the existence of seagrass meadows and a narrow fringe of mangroves. It Figure 1. Map of Roebuck Bay, in North Western Australia, with the study sites indicated as TB (Town Beach), OT (One is a zone used by the community as a recreational area. Tree) and SCC (south of Crab Creek). The other two sites. One Tree and south of Crab Creek 172 Estrella et al.: Potential effects of Lyngbya majuscula blooms. Roebuck Bay, WA are characterised by muddy sediments (Pepping et al. During these observations the following variables 1999, Piersma et al. 2006) and a wider fringe of mangal. were recorded: 1) number of pecks (only the tip of the The use of One Tree as recreational area is more bill entered the substratum), 2) number of probes, 3) restricted and the mud flats south of Crab Creek are number of successful prey captures, 4) prey type seldom visited by humans, as they can only be accessed (unidentified prey were excluded from diet analysis), 5) by boat at high tide. depth of probes and 6) depth of captured prey. Note that depths for (5) and (6) were recorded as one of the Benthic invertebrate diversity and abundance following three categories: i) only the tip of the bill entered the substratum, ii) less than, or half of the bill To evaluate whether the diversity and abundance of entered the substratum and iii) more than half of the bill benthic invertebrates varied between the end of the dry entered the substratum. The depth of captured prey was season and mid wet season, when Lyngbya majuscula then established in relation to the mean bill length of occurred at high densities at Town Beach, samples of Bar-tailed Godwits in North Western Australia (97.4 mm benthic invertebrates were taken from the three locations for both sexes combined; Wilson et al. 2007). indicated above in November 2009 and February 2010. Consequently, it was considered that when only the tip We followed the methodology used in the Monitoring of the bill entered the substratum, the prey was at a Roebuck Bay Benthos program (MONROEB, de Goeij et depth between 0 and 24.4 mm, when less than or half of al. 2003, de Goeij et al. 2008) which has been used in the the bill entered the substratum, the prey was at a depth bay for the last 14 years. Two stations were defined at between 24.5 and 48.7 mm and when more than half of each site, one 150 m offshore and the second 250 m the bill entered the substratum, the prey was at a depth offshore, perpendicular to the coast. At each station four between 48.8 and 97.4 mm. samples were taken, each one consisting of six 10.3 cm diameter cores, driven 20 cm into the sediment. Therefore Statistical analysis each sample represented a sample surface of 0.05 m2 and Normality and homoscedasticity were tested (Shapiro- each station represented a sampled surface of 0.2 m2. Wilk and Levene's test respectively) for each variable. The samples were sieved on the shore initially with a When normality of the data was not achieved a log10 1 mm sieve to remove most of the coarser sediment and (x+0.1) transformation was applied (Sokal and Rohlf then through a 0.5 mm sieve. The samples were labelled 1995). The differences in abundance of invertebrates, and preserved in 70% ethanol and returned to the probes per minute and prey captured per minute laboratory for processing. All samples were processed between months (fixed factor) and among sites (fixed using a stereomicroscope (10 to 22 X magnification), factor) were analysed using a two-way ANOVA test. removing all individuals, identifying to family level, and Differences in prey captured per minute in relation with recording abundance of each family. prey depth were analysed using one-way ANOVA. The information gathered from both stations in each When analyses showed significant differences, post-hoc site was pooled together following de Goeij et al. 2003, tests (parametric Tukey's test) were used to determine where the authors compared the abundance and amongst which months or sites differences existed. diversity of benthic species between both stations in two Values are presented as means ± SE, unless stated sampling sites of Roebuck Bay and obtained similar otherwise. Statistical significance was set at P < 0.05. All results. Diversity was determined using the Shannon- univariate statistical tests were conducted using Statistica Wiener diversity index. 7.0 (StatSoft. Inc., Tulsa, Oklahoma, USA). Differences in the composition of the benthic Shorebird foraging behaviour and prey invertebrate assemblage among sites with and without To evaluate any differences in shorebird foraging Lyngbya were explored using non-metric behaviour between the end of the dry season and mid multidimensional scaling (nMDS) on square root wet season, when Lyngbya majuscula occurred at high transformed data, using the adjusted Bray-Curtis densities in Town Beach, observations of Bar-tailed similarity coefficient (Clarke 1993). The statistical Godwits Limosa lapponica chosen randomly and foraging significance of these differences was determined by actively were made in November 2009 and February 2010 analysis of similarities (ANOS1M; Clarke 1993). All at Town Beach and One Tree stations. Bar-tailed Godwits multivariate analyses were conducted using PRIMER v6 are long distance migrant animals and human induced (PRIMER-E Ltd., Lutton, Ivybridge, UK). changes in their non-breeding habitats could have detrimental effects at a population level, as has been proven for other long distant migratory shorebirds Results (Piersma 2006). Each individual was followed during a three-minute Benthic invertebrate diversity and abundance period through a Kowa 25 x 60 telescope (nTBNov= 32; nTBFi;b= 28; nOTNov= 25; nOTF.,b =30) three hours before and A total of 1057 and 3389 benthic invertebrates were after low tide. Similar numbers of observations were collected in November 2009 and February 2010 taken throughout the daylight period (5-19 GMT) before respectively. Of these, 11 main invertebrate taxa were and after low tide to evade the potential mudflat identified. Polychaete worms compromised more than exposure period effect on feeding rates (Rogers and de 30% and bivalves more than 20% of the total fauna in Goeij 2006). To avoid pseudo-replication (Hulbert 1984), November. In February more than 40% of the fauna were each new bird selected for observation was at least 20-40 sipunculids and almost 24% were gastropods. The total m from the previous individual. abundance of macrobenthos in November was 1602.5, 173 Journal of the Royal Society of Western Australia, 94(2), June 2011 x 2.0-. T5 O c 05 . - (0 JC CO 0.0-1-t- NOV FEB Figure 2. Mean values (±SE) of the Shannon-Wiener diversity index for benthic invertebrates in Town Beach (TB), One Tree (OT) and south of Crab Creek (SCC) in Roebuck Bay, North Western Australia in November 2009 and February 2010. 650.0 and 67.2 individuals per m2 for Town Beach, One Creek, but there was a significant decline in diversity in Tree and south of Crab Creek respectively. In February Town Beach from November to February (Fig. 2). the total abundance was 5117.5, 1437.5 and 88.4 There were significant differences among sites for all individuals per m2 for Town Beach, One Tree and south the taxa studied (Table 1). Polychaetes, tanaids, of Crab Creek respectively. ostracods, ophiurids (brittle stars) and isopods were Diversity of invertebrates was significantly different significantly more abundant in Town Beach than in the among sites (two-way ANOVA: F, = 5.6 P < 0.05), other two stations (Table 1, Figures 3a, 3b, 3c, 3d, 3e). between months (two-way ANOVA: F2= 35.0 P < 0.0001) Bivalve abundance was lower south of Crab Creek in and also among sites x months (two-way ANOVA: F2 = both months (Table 2, Fig. 3f). The abundance of 4.6 P < 0.05). Diversity of invertebrates was significantly scaphopods was higher in One Tree than in the other lower at the station south of Crab Creek than in the other two stations (Table 2, Fig. 3g). two stations in November and February (Fig. 2). There There were significant differences in polychaete, were no changes in invertebrate diversity between brittle star, gastropod and sipunculid abundance November and February in One Tree and south of Crab between November and February (Table 1). There was a Table 1 Table 1: Differences in the mean abundance of invertebrates between November 2009 and February 2010 in Town Beach, One Tree and south of Crab Creek in Roebuck Bay, North Western Australia. Asterisks indicate differences between months, among sites or among sites x months (*: p < 0.05; **: p < 0.001; ***: p < 0.0001; n.s.: non-significant). Taxa Site Month Site x Month F P F P F P *(cid:9733)* *** Polychaeta 25.97 45.91 0.69 n.s. Crabs 5.16 ** 0.85 0.37 n.s. n.s. Bivalves 29.22 *** 0.76 0.49 n.s. n.s. Gastropods 9.38 *** 3.77 *** 3.79 *** Amphipods 9.44 *** 0.69 24.59 n.s. •kick Ophiurids 34.54 (cid:9733)** 12.65 4.03 k Ostracods 10.29 **(cid:9733) 0.40 0.67 n.s. n.s. Isopods 8.50 (cid:9733)** 1.08 1.08 n.s. n.s. Sipunculids 73.07 *** 126.69 *** 73.07 *** Tanaids 55.93 *** 0.26 0.26 n.s. n.s. Scaphopods 7.87 ** 0.59 0.65 n.s. n.s. 174 Estrella et al.: Potential effects of Lyngbya majuscula blooms. Roebuck Bay, WA f) 400 -| E 300 • in > 200 - (>0 5 100 - 0 - g) h) 300 n i) - 7n —•—TB 2 —(cid:9632)— OT O 50 - a-.- see 0 Nov Feb Figure 3. Mean abundance (±SE) of benthic invertebrate taxa grouped as a) polychaetes, b) tanaids, c) ostracods, d) brittle stars, e) isopods, f) bivalves, g) scaphopods, h) gastropods, i) sipunculids (as log (v+0.1)), j) Amphipods and k) crabs in Town Beach (TB), One Tree (OT) and south of Crab Creek (SCC) in Roebuck Bay, North Western Australia, in November 2009 and February 2010. Table 2 Table 2: Differences in the number of probes per minute and prey captured per minute by Bar-tailed Godwits Limosa lappcmica in Town Beach and One Tree between November 2009 and February 2010 in Roebuck Bay, North Western Australia. Asterisks indicate differences between months, among sites or among sites x months (*: p < 0.01; **: p < 0.001; ***• .p < 0.0001; n.s.: non-significant). Site Month Site x Month F P F P F £ Probes fmln 9.32 89.61 MM 5.66 *** «•* Prey! min 105.63 31.35 3.28 n.s. 175 Journal of the Royal Society of Western Australia, 94(2), June 2011 Site (cid:9660) OT (cid:9632) TB (cid:9830) SCC Similarity - 40 Figure 4. n-MDS ordinations using the adjusted Bray-Curtis similarity measure on square root transformed abundance data from core samples collected in Town Beach (TB), One Tree (OT) and south of Crab Creek (SCC) in Roebuck Bay, North Western Australia, in November 2009 (N) and February 2010 (F). significant increase in the abundance of polychaetes in was significantly higher than in all other samples except all the stations from November to February (Fig. 3a). in One Tree in February, whereas the abundance of There was also a significant increase in the abundance of amphipods was also high (Table 1, Fig. 3j). There was a gastropods and sipunculids at Town Beach between decrease in brittle stars between November and February November and February; the abundance of both taxa was in Town Beach. The abundance of brittle stars in Town significantly higher in Town Beach in February than it Beach in November was significantly higher than in all was at the other stations at any time (Table 1, Figures 3h, other samples, whereas in February the abundance of 3i). In contrast there was a decrease in amphipods brittle stars in Town Beach was similar to the abundance between November and February in Town Beach; the of brittle stars in One Tree in November (Table 1, Fig. abundance of amphipods in Town Beach in November 3d). There was no significant change in abundance of crabs at any site between both months (Table 1, Fig. 3k). Ordination analysis of the benthic invertebrate a) 25 abundance data showed that Town Beach samples from February grouped together in a distinct and coherent group separate from the rest of the samples of Town Beach sampled in November and the samples of One Tree and south of Crab Creek sampled in November and February (Fig. 4). The ANOSIM test also showed that there was a significant difference among tire sites with Lyngbya in February (Town Beach) and the sites without Lyngbya in February and November (Global R = 0.64, P = 0.1). ' Shorebird foraging behaviour and prey There were significant differences in the number of probes and prey captured per minute between Town Beach and One Tree and between November and February. Ffowever the number of probes per minute in Town Beach and One Tree were similar in February (Table 2 and Fig. 5a and 5b). NOV FEB There were also significant differences in the number Figure 5. Mean (±SE) number of probes and prey capture per of prey captured per minute depending on the depth of minute of Bar-tailed Godwit feeding on benthic invertebrates in Town Beach (TB) and One Tree (OT) in Roebuck Bay, North captured prey in both sites in both months (Fig. 6). Western Australia, in November 2009 and February 2010. Godwits captured more prey when they fed on deeper- 176 Estrella et al.: Potential effects of Lyngbya majuscula blooms. Roebuck Bay, WA 0-24.4mm 24.5-48.7 mm 48.8-97.4 mm 0-24.4mm 24.5-48.7 mm 48.8-97.4 mm NOV FEB Figure 6. Mean number (±SE) of prey captured per minute by Bar-tailed Godwit depending on the depth of captured prey in Town Beach (TB) and One Tree (OT) in Roebuck Bay, North Western Australia, in November 2009 and February 2010. Asterisks indicate significant differences in the number of prey captured among the different depths in each site for each month (One-way ANOVA *: p < 0.05, ** p < 0.001, *** p < 0.0001). Tire percentage number on top of each bar indicates the percentage of prey captured at each depth in each site for each month. TB November TB February 9.09 364 52.73 OT November 11.11 2.22 86.67 (cid:9632) Polychaetes (cid:9633) Crabs (cid:9633) Bivalves K Sipunculids (cid:9633) Mantis shrimp Figure 7. Percentages of the different prey captured by Bar-tailed Godwit feeding in Town Beach and in One Tree in Roebuck Bay, North Western Australia in November 2009 and February 2010. The percentages have been obtained from direct observations of Bar¬ tailed Godwits feeding actively three hours before and after low tide. 177 Journal of the Royal Society of Western Australia, 94(2), June 2011 buried prey in both months in both stations (Fig. 6). almost 50% of Bar-tailed Godwit prey was captured at a However, although most of the prey (>55% of captured depth between 24.5 and 48.7 mm, and sipunculids were prey) were captured in the 48.8 to 97.4 mm depth the main prey item. Sentinel crabs, the most abundant category in both sites in November and in One Tree in crab in the tidal flats of Roebuck Bay (de Goeij et al. 2003; February, in Town Beach in February 48% of the prey de Goeij et al. 2008; Piersma et al. 2006) probably hide in were captured in the 24.5 to 48.7 mm depth category their borrows at a higher depth than sipunculids, found in Town Beach only in the first centimetres of the (Fig- 6). sediment (SME personal observations). As in other In November, the most common prey for Bar-tailed situations, this change in behaviour suggests that Godwits were crabs at both Town Beach and One Tree. godwits used an opportunistic foraging strategy (Davis The second most common prey were polychaetes and and Smith 2001; Skagen 2006) to exploit the available, bivalves in Town Beach and One Tree respectively (see high density and low mobile sipunculids. However the Fig. 7). In February, crabs were also the most common implications of this shift in prey on this long distance prey for godwits in One Tree, whereas in Town Beach migratory bird with high energetic demands need to be sipunculids were most commonly taken, followed by studied in depth to fully understand the potential crabs (see Fig. 7). impacts of Lyngbya presence on shorebirds. For example, if sipunculids have a lower energetic value per individual than more profitable prey items (i.e. crabs and Discussion polychaetes) this may affect the ability of birds to accumulate energy reserves. Also, the fact that godwits Nutrient enrichment can significantly alter capture more prey per minute in Town Beach than in biodiversity, producing for example shifts in assemblages One Tree does not mean that the actual energy intakes of primary producers and favouring cyanobacterium are higher at Town Beach. Shorebirds can achieve higher blooms which are associated with episodes of anoxia and intake rates in sites where they capture fewer but more hypoxia. Town Beach was the only site where Lyngbya profitable prey (Rogers and de Goeij 2006). was present in February, and it was the only site where the diversity of benthic invertebrates showed a Finally based on these initial results a more in depth significant decrease between November and February. study is currently underway, involving more sampling This appears to be linked with the dramatic increase in occasions, using stable isotopes analysis, mapping abundance of sipunculids (from 0 to 3157.5 sipunculids Lyngbya extension and assessing nutrient concentrations per m2) and gastropods (from 82.5 to 1715 gastropods per in sediments to better elucidate the effects of Lyngbya m2) in Town Beach, both taxa considered as being blooms on benthic fauna, shorebird foodwebs and tolerant of anoxic conditions (Langenbuch and Portner possible relationships with nutrient sources. 2004; Vaquer-Sunyer and Duarte 2008). Also, while the community assemblage of Town Beach did not appear different to the other two sites in November, it was Acknowledgements: This project is funded by the Western Australian Natural Resource Management grant 09060, the Department of significantly different in February. Overall, our Environment and Conservation (DEC Broome Regional Manager, Troy preliminary results suggest that Lyngbya blooms are Sinclair and DEC West Kimberley district manager Alan Byrne), and the affecting the benthic invertebrate community on some Port of Broome Authority (Port of Broome CEO Captain Vic Justice). SME areas of Roebuck Bay. These results are in line with what is supported by a Post-doctoral fellowship (EX2008-0500) from the Spanish Ministry of Science and Technology. This project would not be was found in Moreton Bay (Queensland), where Lyngbya possible without the logistical support of DEC-Broome, the Broome Bird blooms also affected significantly the abundance of Observatory, the Australian Wader Studies Group, the Global Flyway several benthic invertebrates (Garcia and Johnstone Network, the Broome Hovercraft and the Roebuck Bay Working Group. 2006). Nevertheless changes in the distribution and Much of the field work has been done in collaboration with Chris Hassell, Clive Minton, Kingsley Miller, Thomas de Silva, Adrian Boyle, Grant and abundance of benthic organisms could also be attributed Clare Morton and many volunteers. John Curran and Fiona Bishop have to natural seasonal patterns. For example, the changes assisted along the entire project. The benthic invertebrate samples were observed in the abundance of polychaetes appear to be taken under the licences to take fauna for scientific purposes number more related to expected seasonal variation in a tropical SF007116 and SF007246 of the Department of Environment and tidal flat, where higher densities occur in the wet season Conservation of Western Australia. Tire shorebird observational study was approved by the Animal Ethics Committee of the University of (Metcalfe and Glasby 2008). Western Australia (File ref.:F18979). Therefore, a more detailed benthic sampling program with more sampling events, including environmental References variables such as nutrient concentrations and sediment grain size as well as better taxonomic resolution is Ahern K S, Ahem C R & Udy J W 2008 In situ field experiment required in order to provide a more precise conclusion. shows Lyngbya majuscula (cyanobacterium) growth Apart from observed changes in polychaetes, there stimulated by added iron, phosphorus and nitrogen. Harmful Algae 7: 389—404. were no significant changes in the abundance of the other two main Bar-tailed Godwit prey items. Although there Albert S, O'Neil J M, Udy J W, Ahern K S, O'Sullivan C M & Dennison W C 2005 Blooms of the cyanobacterium Lyngbya was no apparent Lyngbya induced change in prey of majuscula in coastal Queensland, Australia: disparate sites, godwits, there was a change in godwit foraging common factors. 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