THE LONG MUD Benthos and shorebirds of the foreshore of Eighty-mile Beach, Western Australia Report on the ‘Anna Plains Benthic Invertebrate and bird Mapping 1999’ (ANNABIM-99) Edited by Theunis Piersma1,2, Grant B. Pearson3, Robert Hickey4 & Marc Lavaleye1 1Department of Marine Ecology and Evolution,Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, 1790 AB Den Burg, Texel, The Netherlands, E-mail: [email protected] 2Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands 3Western Australian Department of Conservation and Land Management (CALM), WA Wildlife Research Centre, P.O. Box 51, Wanneroo, WA 6065, Australia, E-mail: [email protected] 4Department of Geography and Land Studies, Central Washington University, Ellensburg, WA 98926, U.S.A., E-mail: [email protected] With contributions from Michelle Crean (Curtin University of Technology), Petra de Goeij (NIOZ), Pieter J.C. Honkoop (University of Sydney, NIOZ), Maria Mann (Environs Kimberley), Danny I. Rogers (Charles Sturt University) and the Landscope-expeditioners ROYAL NETHERLANDS INSTITUTE FOR SEA RESEARCH (NIOZ), TEXEL WESTERN AUSTRALIAN DEPARTMENT OF CONSERVATION AND LAND MANAGEMENT (CALM) ENVIRONS KIMBERLEY, BROOME CENTRAL WASHINGTON UNIVERSITY, ELLENSBURG, WA, USA TABLE OF CONTENTS SUMMARY . 1 SAMENVATTING . 3 1. PROLOGUE . 5 Grant Pearson 2. INTRODUCTION . .7 Theunis Piersma & Grant Pearson 3. METHODS, ORGANIZATION AND LOGISTICS . 9 Grant Pearson, Maria Mann & Theunis Piersma 4. ACKNOWLEDGEMENTS . 15 5. PERSONAL ACCOUNTS AND EXPEDITION SONGS . 21 Fiona Elizabeth Joshua, Jack Robinson, Marc Lavaleye and others 6. GENERAL DESCRIPTION OF THE STUDY AREA . 51 Grant Pearson, Robert Hickey & Pieter J.C. Honkoop 7. SPATIAL ANALYSIS AT EIGHTY-MILE BEACH . 63 Robert Hickey, Michelle Crean, and Suzanne Wade 8. ATLAS OF THE MACROZOOBENTHIC FAUNA . 73 Marc Lavaleye, Grant Pearson, Theunis Piersma & Petra de Goeij 9. INTERTIDAL BENTHIC COMMUNITY STRUCTURE: ROLE OF SEDIMENT CHARACTERISTICS . 151 Pieter J.C. Honkoop, Grant Pearson, Theunis Piersma & Marc Lavaleye 10. DISTRIBUTION OF SHOREBIRDS ALONG EIGHTY-MILE BEACH . 163 Danny Rogers 11. MANAGING THE UNIQUE MARINE BIODIVERSITY AT EIGHTY MILE BEACH . 207 Grant Pearson, Theunis Piersma & Robert Hickey 12. REFERENCES . 215 THE LONG MUD 1 SUMMARY 1. Eighty-mile Beach is a 230 km long linear identification. Anthozoans, decapods, gas- sand-coast. A beach of 100-500 m width is bor- tropods, bivalves, scaphopods, echinoids, dered by 0.5 to 4 km wide intertidal mudflats. The holothurians and hemichordates were classified intertidal zone is estimated to comprise more to species level, polychaetes and crustaceans to than 60,000 ha (600 km²) of mud and sand that family-level and nemerteans and sipunculids only are exposed by semidiurnal tides with a range of to phylum-level. At each grid point a sediment about 6 m. core was also taken with a diameter of 4.4 cm to a depth of 10 cm. Samples were transferred to a 2. Eighty-mile Beach is known for its accumula- plastic bag, labelled and stored until grain size tions of tropical seashells (from deep water) and analysis in the laboratory. also as a key nonbreeding area for noerthern hemisphere shorebirds. About half a million 5. We identified 112 different taxa, and for most roosting shorebirds have been counted in recent of the taxa, length-frequency diagrams and distri- years, including 50% of the world’s Great Knots bution maps are presented in this report. Forty of Calidris tenuirostris. In February 2004 more than the taxa were not previously found during the ex- 2 million Oriental Pratincoles Glareola mal- tensive macrozoobenthic surveys of Roebuck divarum used Eighty-maile Beach as a daytime Bay. Among these were several bivalve species roost. (an unknown Tellina, Theora fragilis and Paphies cf. altenai), the relatively large Columbellid snails 3. Based at the Anna Plains homestead, a team (Mitrella essingtonensis), the tiny Ringicula snail comprised of 72 volunteers (including 8 and a tiny tuskshell (Polyschides gibbosus). Landscope expeditioners, 8 Notre Dame Among the bristle worms (Polychaeta), the 5 cm University students, 33 local volunteers, 7 logisti- large Pectinaria or gold combs were totally new, cal support people and 16 science volunteers) while clumps of the reef-forming Sabellariidae and 8 scientific co-ordinators, visited 818 inter- were frequently found near the low-water line. tidal sample sites on the Eighty-mile Beach fore- These tube-living Sabellaria are peculiar to me- shore between 8 and 22 October 1999. The sam- chanically undisturbed sedimentary shores. New ple stations were laid out in seven grid-sections to the group of Cnidaria were the sea pens with 200 m intersections along 80 km of the (Pennatulacea) and the burrowing sea anemone beach. The northernmost section was found 10 with its parasitic epitonid snails. A flat sanddollar km north of the Anna Plains entry to the beach, (Arachnoides tenuilus) and a sea cucumber the southernmost 65 km to the south of the entry. (Protankyra verrilli) were also new. At each of the sampling stations samples were taken to determine de densities of macrozooben- 6. Sediments were courser at the highest inter- thic species and grain size distributions. The 818 tidal level and became finer towards the low wa- stations yielded almost 19,000 individual inverte- ter line. Benthic assemblages also differed brates, which were all counted, measured and among tidal heights, a change mainly due to identified to various taxonomic levels. In addition, echinoids and polychaetes that increased in num- shorebird counts were made along the beach at ber towards the lower tidal levels. There was an high tide, and on the different grid-sections during alongshore gradient in the characteristics of sedi- low tide. ments and benthic assemblages as well. Although each section along the beach supported 4. To collect benthos, at each sampling station a unique collection of macrozoobenthic inverte- three cores with a diameter of 10.2 cm (1/120 m²) brates, the distribution of sediments and the were taken to a maximum depth of 30 cm (less if structure of benthic assemblages were quite the corer hit a shell or rock layer and no benthos poorly correlated. This may partly be explained could be expected to live deeper). The sediment by tropical cyclone Vance, which hit the coast of was sieved on the spot over a sieve with a mesh- Western Australia only a few months before our size of 1 mm. All material retained on the sieve study and may have lead to extensive reworking was quantitatively transferred into a plastic bag of the intertidal sediments. and brought to the laboratory for sorting and 2 hier komt de hoofdstuktitel 7. Despite the superficially uniform appareance of 8. In the final chapter we review the management Eighty-mile Beach, the different stretches of the issues of Eighty-mile Beach, and make some rec- coast were important for different shorebird ommendations based on the data accumulated in species. On a broad scale, the distribution of this report. shorebirds was positively related to the abun- dance of their presumed prey. The numbers of birds counted on Eighty-mile Beach at high tide and their species composition, corresponded fair- ly well with the numbers and species composition of shorebirds seen on the intertidal flats at low tide. THE LONG MUD 3 SAMENVATTING 1. Eighty-mile Beach is een 230 km langgerekt 4. Om de bodemfauna te verzamelen, werden op kustgebied. Het 100-500 meter brede zandstrand ieder monsterpunt met behulp van een steekbuis grenst aan een 0,5 tot 4 km breed waddenge- met een diameter van 10.2 cm (1/120 m2) mon- bied. De getijdezone omvat meer dan 60.000 ha sters genomen tot een maximale diepte van 30 (600 km2) zand en modder, waar een getijcyclus cm (maar minder diep wanneer een schelplaag van 12,5 uur en een getijrange van zo’n 6 m de geraakt werd waaronder toch geen benthos kan dienst uitmaken. leven). Het sediment werd ter plekke gezeefd over een zeef met een maaswijdte van 1 mm. Al 2. Eighty-mile Beach is bekend vanwege zijn het materiaal dat achterbleef op de zeef werd in enorme rijkdom aan tropische schelpen (af- een plastic zakje gedaan en naar het laboratori- komstig uit dieper water) maar evenzeer als één um gebracht om direct te worden gesorteerd en van de belangrijkste niet-broedgebieden voor geidentificeerd. Zeeanemonen, garnalen, slak- wadvogels, die op het noordelijke halfrond, in de ken, tweekleppige schelpdieren, olifantstanden, arctis, broeden. In de afgelopen jaren zijn er zo’n stekelhuidigen, zeekomkommers en hemichorda- half miljoen wadvogels geteld, waaronder 50% ten werden geclassificeerd tot soort-niveau, bor- van de wereldpopulatie van de Grote Kanoet stelwormen en kreeftachtigen tot op familie-ni- Calidris tenuirostis. In februari 2004 werd het veau en nemertijnen en sipunculiden alleen tot strand van Eighty-mile Beach door meer dan op phylum-niveau, Op ieder monsterpunt werd twee miljoen Vorkstaartplevieren Glareola maldi- ook een sedimentmonster genomen met een varum gebruikt als tijdelijke rustplaats. steekbuis met een diameter van 4,4 cm en tot op een diepte van 10 cm. Deze monsters werden in 3. Vanuit de thuisbasis ‘Anna Plains Station’, een plastic zak gedaan, van een label voorzien vond van 8 tot 22 oktober 1999 een expeditie en opgeslagen totdat de korrelgrootte analyses in plaats op het wad van Eighty-mile Beach. Een het lab werden gedaan. team bestaande uit 72 vrijwilligers (inclusief 8 Landscope-expeditieleden, 8 studenten van de 5. We identificeerden 112 verschillende taxa Notre Dame Universiteit, 33 lokale vrijwilligers, 7 waarvan voor de meeste in dit rapport lengte-fre- logistieke krachten en 16 wetenschappers) en 8 quentie diagrammen en verspreidingskaartjes wetenschappelijke co-ordinatoren, bemonsterde zijn gepresenteerd. Veertig van de taxa waren in 818 monsterpunten (stations). Op zeven lokaties voorgaande jaren niet eerder gevonden in langs 80 km strand werd een grid-bemonstering Roebuck Bay, gedurende de extensieve macro- gedaan.