Siphonophores from surface waters of the Colombian Pacific Ocean

Siphonophores are colonial hydrozoans that feed on zooplankton including fish larvae, and occur throughout the world’s oceans from surface waters to ocean depths. Here we describe the composition of hyponeustonic siphonophores (0 – 3 m depth) from the tropical Colombian Pacific Ocean based on 131 plankton samples collected between June – October from 2001 – 2004. Samples were dominated by species of Calycophorae, with only three species of Physonectae identified, consistent with their deeper depth distribution. Muggiaea atlantica, Chelophyes contorta, Diphyes dispar, and Eudoxoides mitra were the most common of the 21 species identified. We found moderate structuring of the siphonophore community by the salinity gradient from inshore to offshore, and greater richness during the night because of diel vertical migration. Temperature did not play a significant role in structuring siphonophore communities, perhaps because of the narrow temperature range observed (3.5 8C). We extend the known temperature and salinity range of several species, including M. atlantica up to temperatures of 28.6 8C and salinities down to 24.7. Interestingly, only polygastric stages of M. atlantica were found, suggesting the reproductive stage of M. atlantica in tropical waters might be found in deeper waters. Chelophyes appendiculata was rare in our study and C. contorta was common, providing evidence they have a potential allopatric relationship, with C. contorta replacing C. appendiculata in warm water. Finally, we found siphonophore abundance was positively related to the abundance of copepods and fish eggs, with the top 13 most abundant species all having positive correlations, suggesting siphonophore abundances are tightly controlled by their food

A database of marine phytoplankton abundance, biomass and species composition in Australian waters

There have been many individual phytoplankton datasets collected across Australia since the mid 1900s, but most are unavailable to the research community. We have searched archives, contacted researchers, and scanned the primary and grey literature to collate 3,621,847 records of marine phytoplankton species from Australian waters from 1844 to the present. Many of these are small datasets collected for local questions, but combined they provide over 170 years of data on phytoplankton communities in Australian waters. Units and taxonomy have been standardised, obviously erroneous data removed, and all metadata included. We have lodged this dataset with the Australian Ocean Data Network (http://portal.aodn.org.au/) allowing public access. The Australian Phytoplankton Database will be invaluable for global change studies, as it allows analysis of ecological indicators of climate change and eutrophication (e.g., changes in distribution; diatom:dinoflagellate ratios). In addition, the standardised conversion of abundance records to biomass provides modellers with quantifiable data to initialise and validate ecosystem models of lower marine trophic levels

Two new species of Hydromedusae from Queensland, Australia (Hydrozoa, Leptothecata)

Two new species of small hydromedusae were found during routine monitoring in coastal waters of eastern Australia and are here described. The first, Uribe-Palomino & Gershwin, , from Moreton Bay, Queensland, is placed in its genus because of its possession of both cordyli and eight-fold symmetry. It differs from its congeners in two conspicuous features: firstly, having small, oval split gonads located adjacent to the base of the stomach, and secondly, in its extremely small size at maturity (2 mm bell diameter, compared to the next smallest species at 7 mm). Moreover, it possesses a unique combination of other characters. This species appears to be endemic to Moreton Bay. The second new species, Gershwin & Uribe-Palomino, , from the Great Barrier Reef, Queensland, is placed in its genus because of its two opposite normal tentacles and two opposite marginal clusters of cirri. It differs from its congeners primarily in a more rounded body than the others; the shape, length, and position of its short spindle-shaped, distal gonads; possession of subumbrellar nematocyst clusters; and possession of statocysts. These discoveries bring the total number of species to eight and the total number of species to three. The discovery of these two micromedusae underscores the need for further examination of the often-ignored minute and/or gelatinous fauna

Prey density threshold and tidal influence on reef manta ray foraging at an aggregation site on the Great Barrier Reef

Large tropical and sub-tropical marine animals must meet their energetic requirements in a largely oligotrophic environment. Many planktivorous elasmobranchs, whose thermal ecologies prevent foraging in nutrient-rich polar waters, aggregate seasonally at predictable locations throughout tropical oceans where they are observed feeding. Here we investigate the foraging and oceanographic environment around Lady Elliot Island, a known aggregation site for reef manta rays Manta alfredi in the southern Great Barrier Reef. The foraging behaviour of reef manta rays was analysed in relation to zooplankton populations and local oceanography, and compared to long-term sighting records of reef manta rays from the dive operator on the island. Reef manta rays fed at Lady Elliot Island when zooplankton biomass and abundance were significantly higher than other times. The critical prey density threshold that triggered feeding was 11.2 mg m(-3) while zooplankton size had no significant effect on feeding. The community composition and size structure of the zooplankton was similar when reef manta rays were feeding or not, with only the density of zooplankton changing. Higher zooplankton biomass was observed prior to low tide, and long-term (similar to 5 years) sighting data confirmed that more reef manta rays are also observed feeding during this tidal phase than other times. This is the first study to examine prey availability at an aggregation site for reef manta rays and it indicates that they feed in locations and at times of higher zooplankton biomass

Australia's long-term plankton observations: the integrated marine observing system national reference station network

The Integrated Marine Observing System National Reference Station network provides unprecedented open access to species-level phytoplankton and zooplankton data for researchers, managers and policy makers interested in resource condition, and detecting and understanding the magnitude and time-scales of change in our marine environment. We describe how to access spatial and temporal plankton data collected from the seven reference stations located around the Australian coastline, and a summary of the associated physical and chemical parameters measured that help in the interpretation of plankton data. Details on the rationale for site locations, sampling methodologies and laboratory analysis protocols are provided to assist with use of the data, and design of complimentary investigations. Information on taxonomic entities reported in the plankton database, and changes in taxonomic nomenclature and other issues that may affect data interpretation, are included. Data from more than 1250 plankton samples are freely available via the Australian Ocean Data Network portal and we encourage uptake and use of this continental-scale dataset, giving summaries of data currently available and some practical applications. The full methods manual that includes sampling and analysis protocols for the Integrated Marine Observing System Biogeochemical Operations can be found on-line

Oceanographic drivers of zooplankton biomass and manta ray feeding.

<p>Final generalized additive models for: a) Zooplankton biomass as the response and <i>Trip</i>, <i>Time to low tide</i> and <i>Temperature</i> as predictors (r² = 42.8%, n = 70), and b) Manta ray behaviour (0 = non-feeding; 1 = feeding) as the response and <i>Month</i>, <i>Time to low tide</i> and <i>Temperature</i> as predictors (r² = 5.3%, n = 2973). For each plot, the y-axis is a relative scale, and its magnitude reflects the importance of each variable. Dashed lines and error bars represent 95% confidence intervals.</p

ZooScan system analysis and output.

<p>Using ZooScan to measure the size and composition of zooplankton at Lady Elliot Island: a) Scanned image of a zooplankton subsample, and b) examples of digitally-separated vignettes.</p

Zooplankton size spectra analysis.

<p>Normalised Biovolume Size Spectra of the zooplankton community showing higher biovolume across all size classes (body volume intervals) when reef manta rays are feeding (n = 17) than when non-feeding (n = 12) or absent (n = 21). Dashed lines represent 95% confidence intervals.</p