The origin and age of the Alpha-Mendeleev and Lomonosov ridges in the Amerasia Basin

The results of the bathymetry simulation indicate the emplacement of the Mesozoic Arctic plume into the lithosphere of the Alpha-Mendeleev and Lomonosov ridges. The study also presents a model of the thermal subsidence to the asthenosphere. The calculated coefficients are compared with those obtained for the Greenland-Iceland and Iceland-Faeroe ridges, which were formed in response to hotspot activity. It was shown that the coefficients of the thermal subsidence in the central part of the Alpha-Mendeleev and Lomonosov Ridges are similar to those calculated for the Greenland-Iceland and Iceland-Faeroe ridges. This indicates the thermal regime of the subsidence of the Alpha-Mendeleev and Lomonosov ridges since the Early Miocene and the increased influence of the Arctic plume on the ridge genesis. The ridges are interpreted to have formed over a broad geological timeframe, from the late Cretaceous to the Cenozoic. A geothermal method, which is highly informative in terms of the age of the lithosphere, provides better constraints on the timing of ridge formation. The age estimates for the Alpha-Mendeleev (97–79 Ma) and Lomonosov ridges (69–57 Ma) derived from the geothermal data allowed us to draw a convincing conclusion about the genesis of these ridges.     

Coral communities and reefs from Guerrero,Southern Mexican Pacific

Corals in the Eastern Pacific extend south from the Gulf of California to Ecuador and oceanic Chile, and west from Colombia to Clipperton Atoll. Nevertheless, large stretches of the Mexican Pacific remain fundamentally unstudied. Therefore, to assess the current conditions of coral communities, a coastal fringe ～300 km long (17°40′ N, 101°39′ W to 16°46′ N, 99°49′ W) was surveyed within the Southern Mexican Pacific, between 2005 and 2009. Fifteen stony coral species were identified at 13 coral communities and six Pocillopora‐dominated fringing reefs, with Pocillopora verrucosa and Pocillopora damicornis the primary contributing taxa. Reef development was identified in embayments or behind rocks or islands that offered shelter from northern and northwestern winds. Observations of Pocillopora effusus, Pocillopora inflata, Porites lobata, Pavona clavus, and Pavona varians expanded the species known geographic ranges by several degrees of latitude, suggesting reef building fauna comprised a mixture of widespread and relatively rare Eastern Pacific corals. Results indicated greater live coral cover in the Ixtapa‐Zihuatanejo area (15–73%) than in the Acapulco localities, which had high algal dominance; the reefs in the latter region exhibited high erosion. Regional differences are likely the result of long‐standing anthropogenic pressures around Acapulco since 1950, when it became an important tourist destination. This paper is the first detailed report of ecologically stressed corals and coral reefs from the state of Guerrero on the Mexican Southern Pacific coast.     

The effect of membrane filtration on estimates of microbial ATP in New Zealand freshwaters

Concentrations of microbial ATP in 15 New Zealand lakes were determined using 2 extraction techniques. ATP was found in both the paniculate (>0.45 μm) and dissolved (<0.45 μm) fractions of the water samples. Higher concentrations of paniculate ATP were obtained when ATP was extracted directly from freshwater samples rather than following pre‐concentration on to membrane filters. Recovery of particulate ATP declined with increasing volumes of sample filtered. The magnitude of the filtration effect varied unpredictably between lakes and within lakes with time. Corrections for the presence of dissolved ATP were necessary before estimates of particulate ATP could be made by the direct extraction technique. Concentrations of dissolved ATP up to 1.2 μg L^‐1 were observed. The direct extraction technique is recommended for more accurate determination of particulate ATP in New Zealand freshwaters.     

Diet of landlocked sockeye salmon (Oncorhynchus nerka) and trout in the Waitaki lakes,New Zealand

Landlocked sockeye salmon (Oncorhynchus nerka), ranging in fork length (FL) from 105 to 313 mm, were captured in fine‐mesh gill nets set in the limnetic zone of the Waitaki hydro lakes (44° 30′ S, 170° 10’ E) in the South Island, New Zealand. A total of 443 stomachs was examined and the frequency of occurrence, volume and weight of prey items calculated. In the Ahuriri Arm of Lake Benmore the principal food (54% by weight) was zooplankton (Boeckella dilatata) whereas in the Haldon Arm of Lake Benmore it was larval and juvenile common bullies (Gobiomorphus cotidi‐anus) (73% by volume). In Lake Waitaki in winter, salmon had eaten insects (43% by volume) with smaller amounts of snails (Potamopyrgus antipo‐darum, 23%) and bullies (24%). In Lake Ohau adult insects may be an important food. There were also variations in diet with season and fish size. The stomachs of 147 brown trout (Salmo trutta) and 181 rainbow trout (S. gairdnerii) caught in the same gill nets were also examined. In contrast to sockeye salmon stomachs they contained negligible amounts of zooplankton (< 1% by weight) and large amounts of aquatic insects (50–58% by weight in the Ahuriri Arm of Lake Benmore). Comparisons with juvenile sockeye salmon and kokanee in North American lakes are made. The impact of introductions of sockeye salmon into other New Zealand lakes is discussed.     

Oceanic exchange variability across the continental slope west coast,South Island,New Zealand

Current observations taken at depths between 630 and 830 m from the west coast South Island continental slope exhibit one‐ to four‐weekly periodicities superimposed on the semi‐diurnal tide. These variable flows at 630 m and otter large, longer‐timescale events have a significart onshore/offshore component of flow which leads to a similar transport of alongshore momentum and heat.     

Pfiesteria shumwayae (Pfiesteriaceae) in New Zealand

Pfiesteria shumwayae Steidinger et Burkholder is now known to be present in New Zealand and occurs in estuaries around the country. The presence of Pfiesteria was initially determined by a polymerase chain reaction (PCR)‐based detection assay, using oligonucleotide primers targeted at ribosomal DNA extracted from estuarine water and sediments. Presence was confirmed by isolation from fresh sediments in the presence offish (Oreochromis mossambicus), followed by identification by scanning electron microscopy. The New Zealand isolates of P. shumwayae were ichthyotoxic in bioassays, but there is no historic evidence offish kills in New Zealand associated with the dinoflagellate.     

Gametogenic development and spawning of the razor clam,Zenatia acinaces in northeastern New Zealand

The potential exists for New Zealand to exploit already established markets for razor clams through development of fisheries or aquaculture industries for the New Zealand razor clam, Zenatia acinaces. However, fishery or aquaculture development for Z. acinaces requires an understanding of the reproductive cycle including the timing of gametogenic development and spawning. The reproductive cycle of Z. acinaces was studied over an 11‐month period from May 2000 to March 2001 at Kennedy Bay, Coromandel Peninsula, using qualitative standard histological analysis and quantitative measures of oocytes. Histological analysis indicated that Z. acinaces is dioecious and gametogenic development was synchronous between the sexes. Gametogenesis began in June with gametes maturing quickly and by August/September (late winter/ early spring) most razor clams were ripe. Spawning began as early as September (spring) although spawning mainly occurred during October. By December (summer), nearly all clams were completely spent. From January 2001 most clams could not be sexed as all residual gametes were resorbed. Razor clams remained in this stage during March 2001. Spawning began when the water temperature was around its lowest, c. 15°C. Monthly mean number of eggs/follicle was sensitive to changes in reproductive development, closely following patterns observed in the qualitative stagings. Patterns of monthly mean oocyte diameters did not adequately describe the spawning events observed in qualitative analyses. Sex ratios were equal over the size range (69–99 mm shell length) of clams that could be sexed. The data presented in this study provide valuable information on the timing of spawning events for Z. acinaces, necessary for developing sustainable management strategies and selecting broodstock for aquaculture.     

Notes on the ecology and paleoecology of neothyrls,an endemic New Zealand brachiopod

Neothyris lecticularis (Deshayes, 1839) live mainly south o'f 44°S in waters 90–180 m (extremes 18–384 m) deep where bottom temperatures are always >7°c. Fossil N. “avails” (Hutton, 1886) in the early Pleistocene limestone at Castlepoint (41 °S) are associated with an assemblage of animals generioally the same as the living N. lenticularis assemblage of Foveaux Strait. The granular substrate occupied by the living animals is similar to the matrix of the Castlepoint limestone. Thus the early Pleistocene marine climate in 90–180 m at 43°S may have been about 5°c cooler than it is today; the possible use is mentioned of the presence of the fossil assemblage in studies of palaeoelimates.

Population analysis of living and fossil stocks show a constant bias toward the older age‐groups; this finding is discussed. Various ecological observations are recorded.     

Observational data assimilation in the problem of Black Sea circulation and sensitivity analysis of its solution

The problem of the variational data assimilation of the sea-surface temperature for the model of the Black Sea dynamics has been formulated and numerically studied to reproduce surface heat fluxes. An analysis of sensitivity of the optimal solution to errors in observation data has been conducted. The results of numerical experiments have been presented.     

Gelatinous macroplankton in the Black Sea in the autumn of 2010

In October and November of 2010, the gelatinous macroplankton in the northwestern Black Sea and at the Crimean shelf was represented by the scyphozoan jellyfish Aurelia aurita, three species of ctenophores (Beroe ovata, Mnemiopsis leidyi, and Pleurobrachia pileus), and three species of hydromedusae. A. aurita was more common at the shelf, M. leidyi and P. pileus prevailed at the deeper sea stations, and B. ovata was almost ubiquitous with a biomass from below 1 to 49 g/m² A. aurita, which had an average biomass of 82–224 g/m², was dominant at all the stations. M. leidyi, which had a biomass from below 1 to 115 g/m², was recorded in October at only 14 of the 52 stations and in November at 20 of the 46 stations. The highest biomass of M. leidyi in October (105 to 116 g/m²) was recorded in the deep sea areas; in November, it was also the highest in these areas, but it reached at most 100 g/m². The average daily ration of Aurelia ranged from 19.4 to 27.3 mg/m² in October and from 7.0 to 17.2 mg/m² in November; in both cases, it was insufficient to provide for the minimal physiological requirements. The average daily ration of the Mnemiopsis population (2.8–20.5 mg of zooplankton per m²) was invariably more than sufficient to provide for the minimal physiological requirements. Both predatory species together consumed less than 5% of the daily zooplankton production of the sea.