Experimental assessment of sediment burial in eelgrass Zostera marina in Kiel Bight

Seagrass meadows, one of the world's most important and productive coastal habitats, are threatened by a range of anthropogenic actions. Burial of seagrass plants due to coastal activities is one important anthropogenic pressure leading to the decline of local populations. In our study, we assessed the response of eelgrass Zostera marina to sediment burial from physiological, morphological, and population parameters. In a full factorial field experiment, burial level (5-20cm) and burial duration (4-16 weeks) were manipulated. Negative effects were visible even at the lowest burial level (5 cm) and shortest duration (4 weeks), with increasing effects over time and burial level. Buried seagrasses showed higher shoot mortality, delayed growth and flowering and lower carbohydrate storage. The observed effects will likely have an impact on next year's survival of buried plants. Our results have implications for the management of this important coastal plant.

Parameters of population dynamics and energetics of ctenophore Mnemiopsis leidyi in Sevastopol Bay from January 1995 to March 1996

Population dynamics of abundance and biomass were studied and specific production of population of ctenophore Mnemiopsis leidyi was estimated in the Sevastopol Bay from January 1995 to March 1996. The ctenophores achieved maximum abundance and biomass in July during period of intensive reproduction. Young specimens (<5 mm) contributed during that period as much as 50-87% to total abundance of population. Annually averaged daily specific growth rate was 0.039. Growth, food consumption, and rate of filtration were measured in a laboratory under two concentrations of food (Acartia clausi and Moina micrura: 60 and 100 specimens per liter, 0.35 and 0.60 mg wet weight/l). Both concentrations sustained growth of animals with dry weight less than 20 mg. However these concentrations were insufficient to sustain growth of larger ctenophores. Specific growth rate of the ctenophores with dry weight <20 mg under favorable food conditions was 0.20-0.30 l/day. Specific growth rate of the ctenophores in the Sevastopol Bay never exceeded 0.093 l/day, mean biomass of fodder zooplankton in the bay being 90 mg/m**3 in terms of wet weight. Hence a conclusion was made that population of M. leidyi in the bay was limited by lack of food.

Feeding parameters of copepods from upwelling areas

Feeding patterns of mass herbivorous copepods in upwelling areas are investigated. Daily rations and aspects of their formation are examined in Calanoides carinatus (Benguela upwelling), Calanus pacificus (off the California coast), and Calanus australis (Peru upwelling). Rations were calculated based on gut plant pigment contents obtained at daily stations using laser spectrofluorometry, experimental data on the rate of gut evacuation and data on the carbon/chlorophyll ratio in phytoplankton and particulate matter at the respective stations. When phytoplankton was abundant, diel feeding rhythms were not pronounced and gut pigment level was high during the entire 24-h period. When phytoplankton biomass was low, distinct feeding rhythms were pronounced with a nocturnal maximum. During active upwelling intensive feeding on phytoplankton supports energy (respiration) and plastic (growth, development, reproduction, accumulation of reserves) metabolism of copepods. When upwelling was inactive, the surface part of the population feeds less actively and is able only partially to cover its energy expenditures. The actively growing and reproducing populations of C. pacificus and C. carinatus may consume close to 20% of primary production, whereas the inactive population of C. australis consumed only 0.2% of primary production when upwelling weakened.

Pigments, phytoplankton and its production parameters in the Obskaya Guba and adjacent Kara Sea in the latest September 2007

Material was collected in the Ob River estuary and the adjacent shallow Kara Sea shelf between 71°14.0'N and 75°33.0'N at the end of September 2007. Latitudinal zonation in phytoplankton distribution was demonstrated; this zonation was determined by changes in salinity and concentration of nutrients. Characteristic of the phytocenosis in the southern desalinated zone composed of freshwater diatom and green algae species were high population density (1500000 cells/l), biomass (210 ?g C/l), chlorophyll concentration (4.5 ?g/l), and uniform distribution in the water column. High primary production (~40 ?g C/l/day) was recorded in the upper 1.5 m layer. The estuarine frontal zone located to the north had a halocline at depth 3-5 m. Freshwater species with low abundance (250000 cells/l), biomass (24 ?g C/l), and chlorophyll concentration (1.5 ?g/l) dominated above the halocline. Marine diatom algae, dinoflagellates, and autotrophic flagellates formed a considerable part of the phytocenosis below the halocline; community characteristics were two-fold lower as compared with the upper layer. Maximal values of primary production (~10 ?g C/l/day) were recorded in the upper 1.5 m layer. The phytocenosis in the seaward zone was formed by marine alga species and was considerably poorer as compared with the frontal zone. Assimilation rates of carbon per chlorophyll a at the end of the vegetation season within the studied area were low, average 0.4-1.0 ?g C/?g Chl/hour in the upper layer and 0.03-0.1 ?g C/?g Chl/hour below the pycnocline.

Biogeochemical parameters and processes in waters and bottom sediments of the Chukchi Sea

Study of biogeochemical processes in waters and sediments of the Chukchi Sea in August 2004 revealed atypical maxima of biogenic element (N, P, and Si) concentrations and rate of microbial sulfate reduction in the surface layer (0-3 cm) of marine sediments. The C/N/P ratio in organic matter (OM) of this layer does not fit the Redfield-Richards stoichiometric model. Specific features of biogeochemical processes in the sea are likely related to the complex dynamics of water, high primary produc¬tivity (110-1400 mg C/m**2/day), low depth of the basin (<50 m for 60% of the water area), reduced food chain due to low population of zooplankton, high density of zoobenthos (up to 4230 g/m**2), and high activity of microbial processes. Drastic decrease in concentrations of biogenic elements, iodine, total alkalinity, and population of microorganisms beneath the 0-3 cm layer testify to large-scale OM decay at the water-seafloor barrier. Our original experimental data support high annual rate of OM mineralization at the bottom of the Chukchi Sea.