Observations on the ecology of Pleurobrachia pileus (Ctenophora) in the southern Benguela ecosystem

The vertical distribution, abundance and size composition of a population of Pleurobrachia pileus was studied during a six-day drogue study conducted off the west coast of South Africa in February 1995. The population was centred in deep water, possibly because of the presence of a potential predator, Beroe sp., at shallower depths. The population of P. pileus failed to display clear patterns of migration, although nocturnal recruitment from deeper water resulted in a deepening of the depth of occupation then. The population was dominated by individuals <4 mm polar diameter, and large animals were confined to the upper water layers. These results are discussed with reference to possible spawning activities. Using published equations relating size to clearance rates, it was estimated that the population could remove up to 27% of integrated mesozooplankton standing stocks, and in excess of 100% (293%) at some depths.Web of Scienc

OBSERVATIONS ON THE ECOLOGY OF PLEUROBRACHIA PILEUS (CTENOPHORA) IN THE SOUTHERN BENGUELA ECOSYSTEM

The vertical distribution, abundance and size composition of a population of Pleurobrachia pileus was studied during a six-day drogue study conducted off the west coast of South Africa in February 1995. The population was centred in deep water, possibly because of the presence of a potential predator, Beroe sp., at shallower depths. The population of P. pileus failed to display clear patterns of migration, although nocturnal recruitment from deeper water resulted in a deepening of the depth of occupation then. The population was dominated by individual

Accommodating Dynamic Oceanographic Processes and Pelagic Biodiversity in Marine Conservation Planning

Pelagic ecosystems support a significant and vital component of the ocean's productivity and biodiversity. They are also heavily exploited and, as a result, are the focus of numerous spatial planning initiatives. Over the past decade, there has been increasing enthusiasm for protected areas as a tool for pelagic conservation, however, few have been implemented. Here we demonstrate an approach to plan protected areas that address the physical and biological dynamics typical of the pelagic realm. Specifically, we provide an example of an approach to planning protected areas that integrates pelagic and benthic conservation in the southern Benguela and Agulhas Bank ecosystems off South Africa. Our aim was to represent species of importance to fisheries and species of conservation concern within protected areas. In addition to representation, we ensured that protected areas were designed to consider pelagic dynamics, characterized from time-series data on key oceanographic processes, together with data on the abundance of small pelagic fishes. We found that, to have the highest likelihood of reaching conservation targets, protected area selection should be based on time-specific data rather than data averaged across time. More generally, we argue that innovative methods are needed to conserve ephemeral and dynamic pelagic biodiversity

Epipelagic siphonophores off the east coast of South Africa

This work represents the first systematic analysis of the common Siphonophora from the Agulhas Current (South-West Indian Ocean). A total of 56 species of siphonophores was collected from a series of three largely epipelagic cruises between Algoa Bay and the Tugela River along the east coast of South Africa. Although no readily identifiable Cystonectae were observed, four families and nine species of Physonectae were collected. Calycophorae were the most common and abundant siphonophores, and five families and 47 species were recorded. Details of locations where each species was collected are given, but descriptions and illustrations are provided only for taxa that represent new records for the region. African Journal of Marine Science 2005, 27(1): 129–13

Distribution of epipelagic metazooplankton across the Mediterranean Sea during the summer BOUM cruise

The diversity and distribution of epipelagic metazooplankton across the Mediterranean Sea was studied along a 3000 km long transect from the eastern to the western basins during the BOUM cruise in summer 2008. Metazooplankton were sampled using both a 120 mu m mesh size bongo net and Niskin bottles in the upper 200 m layer at 17 stations. Here we report on the stock, the composition and the structure of the metazooplankton community. The abundance was 4 to 8 times higher than in several previously published studies, whereas the biomass remained within the same order of magnitude. An eastward decrease in abundance was evident, although biomass was variable. Spatial (horizontal and vertical) distribution of metazooplankton abundance and biomass was strongly correlated to chlorophyll-a concentration. In addition, a clear association was observed between the vertical distribution of nauplii and small copepods and the depth of the deep chlorophyll maximum. The distinction between the communities of the eastern and western basins was clearly explained by the environmental factors. The specific distribution pattern of remarkable species was also described

Man-induced hydrological changes, metazooplankton communities and invasive species in the Berre Lagoon (Mediterranean Sea, France)

The Berre Lagoon has been under strong anthropogenic pressure since the early 1950s. The opening of the hydroelectric EDF power plant in 1966 led to large salinity drops. The zooplankton community was mainly composed of two common brackish species: Acartia tonsa and Brachionus plicatilis. Since 2006, European litigation has strongly constrained the input of freshwater, maintaining the salinity above 15. A study was performed between 2008 and 2010 to evaluate how these modifications have impacted the zooplankton community. Our results show that the community is more diverse and contains several coastal marine species (i.e., Centropages typicus, Paracalanus parvus and Acartia clausi). A. tonsa is still present but is less abundant, whereas B. plicatilis has completely disappeared. Strong predatory marine species, such as chaetognaths, the large conspicuous autochtonous jellyfish Aurelia aurita and the invasive ctenophore Mnemiopsis leidyi, are now very common as either seasonal or permanent features of the lagoon