Phytoplankton Composition in the Coastal Magnetic Island Lagoon, Western Pacific Ocean (Australia) E
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Transitional Waters Bulletin TWB, Transit. Waters Bull. 7 (2013), n. 2, 145-158 ISSN 1825-229X, DOI 10.1285/i1825229Xv7n2p145 http://siba-ese.unisalento.it Phytoplankton composition in the coastal Magnetic Island lagoon, Western Pacific Ocean (Australia) E. Stanca1*, L. Roselli1, M. Cellamare2, A. Basset1 1Department of Biological and Environmental Sciences and Technologies, University of Salento, SP Lecce-Monteroni, 73100 Lecce, Italy. 2Muséum National d’Histoire Naturelle, UMR 7245 CNRS-MNHN Molécules RESEARCH ARTICLE de Communication et Adaptation des Micro-organismes, Eq. Cyanobactéries, Cyanotoxines et Environnement 12, rue Buffon – CP39, 75231 Paris Cedex 05, France. *Corresponding author: Phone: +39 0832 298889; E-mail address: elena. [email protected] Abstract 1 - Coastal lagoons have traditionally been considered as transitional systems between continental and marine domains. The phytoplankton plays a key role in these aquatic environments, forming the base of the food web and having a substantial function in nutrient dynamics and in the carbon biogeochemical cycle. 2 - Due to their short life cycle, planktonic algae respond quickly to environmental changes and they are thus a valuable indicator of water quality. It is essential to investigate the development of phytoplankton populations to understand the biological functioning and to detect changes in aquatic systems. 3 - Phytoplankton studies in the Australian estuaries and lagoons are relatively scarce. This study has provided a broad perspective and preliminary information on taxonomic structure of phytoplankton guilds for the Magnetic Island Lagoon (Queensland, Australia). This work may provide valuable information of interest to later ecological studies. 4 - In the whole sampling a total of 143 taxa were identified. In terms of species richness, diatoms (Bacillariophyceae, Coscinodiscophyceae, Fragilariophyceae) and dinoflagellates (Dinophyceae) were the most important groups. In taxonomic terms, diatoms were the major contributor to the phytoplankton composition (~ 70%) whereas Dinophyceae were moderately abundant (~23%). Diatoms are a very important component in estuarine and shallow coastal wetlands and they are increasingly being utilized as indicators of environmental change. Keywords: phytoplankton; diatoms; dinoflagellates; taxonomic structure; Magnetic Island; Western Pacific Ocean; Australia. Introduction Directive (WFD) of the European Union Coastal lagoons have traditionally been (Bianchi, 1988; Pérez-Ruzafa et al., 2008). considered as transitional systems between They are characterized by particular continental and marine domains, a features, such as shallowness, relative consideration that has gained in importance isolation from the open sea, usually as a in the context of the Water Framework result of coastal barriers that maintain some © 2013 University of Salento - SIBA http://siba-ese.unisalento.it TWB 7 (2013), n. 2 E. Stanca, L. Roselli, M. Cellamare, A. Basset communication channels or inlets, and the Much work is still needed to unrevel presence of boundaries with strong physical phytoplankton patterns and composition and ecological gradients (UNESCO, 1981). in many remote areas that remain largely Bottoms are usually well irradiated, because unexplored. Magnetic Island lagoon, in of their shallowness, while currents and Queensland (Australia) is one of these. hydrodynamics are closely conditioned by The Australian continent is surrounded by bottom topography and wind affects the entire three oceans and its marine waters, extending water column, promoting the resuspension of over 16 million km2, are amongst the largest materials and nutrients from the sediment in the world (Newton and Boshier, 2001). surface layer. Emergent properties of lagoon The coastal and shelf waters of Australia are ecosystems have recently been reviewed in very diverse in their water temperature, sun comparison with other types of transitional light exposure and nutrient concentrations, waters (Basset et al., 2013). the three key drivers of phytoplankton Due to the fact of being areas with restricted blooms. The large size and variability exchange with the adjacent ocean and thus of the Australian coastal and continental may accumulate nutrients supplied by the shelf waters make the different monitoring surrounding watershed, coastal lagoons are methods of phytoplankton, traditional commonly characterised by high productivity oceanographic sampling and alternative (Taylor et al., 1999). method using satellite ocean color remote Phytoplankton drives the bulk of primary sensing (Blondeau-Patissier et al., 2011). production in most aquatic ecosystems and Algae studies in Australia begun in 1730, when contribute 50 per cent to the global assimilation William Dampier published the first record of organic carbon (Falkowski et al., 1998). of Australian algae. Since then, a number of These photosynthetic organisms plays a key phytoplankton studies covering the oceanic role in aquatic environments, forming the waters, lakes and lagoons have been carried base of the food web and having a substantial out in different regions of Australia (Dakin function in nutrient dynamics and in the and Colefax, 1993; Wood, 1954; Humphrey, carbon biogeochemical cycle (Graham and 1963; Hallegraeff, 1981; Royle, 1985; Wilcox, 2000; Sarmiento and Gruber, 2006; Hallegraeff and Jeffrey, 1984; King et al., Almandoz et al.,2011). 1997; Trott and Alongi, 1999; O’Donohue et Due to their short life cycle, planktonic algae al., 2000; Chan and Hamilton, 2001; Ajani et respond quickly to environmental changes al., 2001, 2002). But compared with the off- and are thus a valuable indicator of water shore research, phytoplankton studies in the quality. To this extent, phytoplankton cell Australian estuaries and lagoons are relatively size and shape represent morpho-functional scarce. Many Australian governments have traits of overwhelming importance (Stanca et established water quality objectives for major al., 2013a); phytoplankton size spectra and estuaries and are developing the sustainable size classes have been shown to have a high management procedures under the various information content to detect environmental water reform initiatives (Liu, 2008). condition change in transitional and coastal Guidelines for all aspects of phytoplankton waters (Sabetta et al., 2008; Lugoli et al., 2012; monitoring in Australian freshwaters has Vadrucci et al., 2013). Then it is essential to been developed at a time when lakes and investigate the development of phytoplankton rivers have become the focus of many water populations to understand the biological resource issues in Australia, in particular functioning of aquatic systems and detect the need to ensure ecosystem sustainability changes in them (Hötzel and Croome, 1999). (Hötzel and Croome, 1999). © 2013 University of Salento - SIBA http://siba-ese.unisalento.it 146 TWB 7 (2013), n. 2 Phytoplankton in Magnetic Island Lagoon Most of the studies were carried out in contains around 40 km of coastline and is the Australian coastal waters, estuaries the seventh largest and the fourth highest of and coastal lagoon but there is no detailed the 600 continental islands in the GBRWHA. information on phytoplankton and their About half of the island (2533 ha) and ecological features in Magnetic Island much of the elevated country is protected Lagoon. Therefore, the present study (under the Queensland Nature Conservation aimed to examine the taxonomic structure Act 1992) as the Magnetic Island National of phytoplankton to provide preliminary Park and there are also two small areas information on the Magnetic Island Lagoon, designated as Conservation Parks. There as a model ecosystem of leaky lagoons are five matters of national environmental characterized by meso-tidal regimes ensuring significance relevant to Magnetic Island. high openness and low water turnover times Specifically, the island is: home or habitat at high tides. to listed threatened species and a threatened ecological community; habitat to listed Material and methods migratory species; part of the Great Barrier Study site Reef World Heritage Area; part of the Great Magnetic Island is an inshore continental Barrier Reef National Heritage place, and island (52 km2) of the GBR located about 8 km surrounded by the Great Barrier Reef Marine offshore from Townsville, in NE Queensland, Park. A variety of marine environments Australia (Fig. 1) (Lewis et al., 2012). occur around the island, including mangrove It is located within the dry tropics region forests, salt marshes, fringing coral reefs of north Queensland and the Great Barrier and seagrass communities; these provide Reef World Heritage Area (GBRWHA) and is important habitat for marine flora and fauna. part of the Townsville City local government Many listed species live in the waters around area. The island is about 5184 ha in size, the island including sea snakes, turtles, Figure 1. Study site. © 2013 University of Salento - SIBA http://siba-ese.unisalento.it 147 TWB 7 (2013), n. 2 E. Stanca, L. Roselli, M. Cellamare, A. Basset dugongs and dolphins (Commonwealth of were: Smith and Tuffen, 1853; Van Heurck, Australia, 2010). 1880-1885; Boyer, 1926; Cupp, 1943; Crosby and Wood, 1958, 1959; Wood et Field procedures and Phytoplankton analysis al., 1959; Subrahmanyan, 1971; Rampi and A hierarchical sampling design was followed, Bernhard, 1978, 1980; Dodge, 1982; Ricard, according to the criteria adopted for a large 1987; Sournia, 1986, 1987; Chrétiennot-