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Diatoms constitute a diverse lineage of unicellular organisms abundant and ecologically important in aquatic ecosystems. Compared to other protists, their biology and taxonomy are well-studied, offering the opportunity to combine traditional approaches and new technologies. We examined a dataset of diatom 18S rRNA- and rDNA- (V4 region) reads from different plankton size-fractions and sediments from six European coastal marine sites, with the aim of identifying peculiarities and commonalities with respect to the whole protistan community. Almost all metabarcodes (99.6%) were assigned to known genera (121) and species (236), the most abundant of which were those already known from classic studies and coincided with those seen in light microscopy. rDNA and rRNA showed comparable patterns for the dominant taxa, but rRNA revealed a much higher diversity particularly in the sediment communities. Peculiar to diatoms is a tight bentho-pelagic coupling, with many benthic or planktonic species colonizing both water column and sediments and the dominance of planktonic species in both habitats. Overall metabarcoding results reflected the marked specificity of diatoms compared to other protistan groups in terms of morphological and ecological characteristics, at the same time confirming their great potential in the description of protist communities.

Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (52–73) Tg N yr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1) Tg C from cell counts and to 89 (43–150) Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 9.2 Tg N yr−1, 18 1.8 Tg C and 590 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about 70%. It was recently established that the most commonly applied method used to measure N2 fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N2 fixation rate upward and may result in significantly higher estimates for the global N2 fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future. The database is stored in PANGAEA (doi:10.1594/PANGAEA.774851).

The global marine fish catch is approaching its upper limit. The number of overfished populations, as well as the indirect effects of fisheries on marine ecosystems, indicate that management has failed to achieve a principal goal, sustainability. This failure is primarily due to continually increasing harvest rates in response to incessant sociopolitical pressure for greater harvests and the intrinsic uncertainty in predicting the harvest that will cause population collapse. A more holistic approach incorporating interspecific interactions and physical environmental influences would contribute to greater sustainability by reducing the uncertainty in predictions. However, transforming the management process to reduce the influence of pressure for greater harvest holds more immediate promise

Coastal and open ocean regions of the Western Tropical South Pacific ocean have been identified as a hotspot of N2 fixation. However, the environmental factors driving the temporal variability of abundance, composition, and activity of diazotrophs are still poorly understood, especially during the winter season. To address this, we quantified N2 fixation rates and the abundance of seven diazotroph phylotypes (UCYN-A1 symbiosis, UCYN-B, UCYN-C, Trichodesmium, Het-1, Het-2 and Het-3) on a monthly basis during two full years (2012 to 2014) at four stations along a coast to open ocean transect in the New Caledonian lagoon. The total nifH gene concentration (sum of all nifH gene copies) clearly decreased from the barrier reef to the shore. Apart from UCYN-B, which peaked at very high abundances (106-108nifH gene copies L-1) at two occasions at the coastal station, the UCYN-A1 symbiosis was the most abundant group at all stations, accounting for 79 % of the total nifH gene copy counts along the transect (average abundance 4.2 ± 10.3 x 104 nifH gene copies L-1). The next most abundant groups were in order Trichodesmium (accounting for 14% of the total nifH gene copies), Het-groups (6% of the total) and UCYN-C (1% of the total). Statistical analyses reveal that the UCYN-A1 symbiosis and Het groups were associated with cold (<25°C) waters, high NOx and PO43-, weak winds from the south (occasionally southwest), while Trichodesmium and UCYN-C were associated with warmer (>25°C) waters, low NOx and PO43- concentrations, strong and (mostly) easterly winds. Average N2 fixation rates over the survey were 6.5 ± 6.7 nmol N L-1 d-1 and did not differ significantly among seasons. The interannual variability was more pronounced with average integrated rates significantly higher the second year of the survey (162 ± 122 μmol N m-2 d-1) than the first year (66 ± 91 μmol N m-2 d-1), likely due to higher seawater temperature. This dataset suggests that seasonality is less pronounced than previously thought, and that relatively high N2 fixation rates are maintained in the New Caledonian lagoon all year long, despite seasonal changes in the diazotroph community composition.

Cooperation and Engagement in the Asia-Pacific Region provides valuable insight into a region that encompasses many important maritime regions, and harbors promising opportunities for maritime cooperation and engagement.

Changes in the invertebrate fauna of a California rocky intertidal community between the period 1931 to 1933 and the period 1993 to 1994 indicate that species' ranges shifted northward, consistent with predictions of change associated with climate warming. Of 45 invertebrate species, the abundances of eight of nine southern species increased and the abundances of five of eight northern species decreased. No trend was evident for cosmopolitan species. Annual mean shoreline ocean temperatures at the site increased by 0.75 degrees C during the past 60 years, and mean summer maximum temperatures from 1983 to 1993 were 2.2 degrees C warmer than for the period 1921 to 1931

In oceanic, coastal, and estuarine environments, an average of 25 to 41 percent of the dissolved inorganic nitrogen (NH4+ and NO3-) taken up by phytoplankton is released as dissolved organic nitrogen (DON). Release rates for DON in oceanic systems range from 4 to 26 nanogram-atoms of nitrogen per liter per hour. Failure to account for the production of DON during nitrogen-15 uptake experiments results in an underestimate of gross nitrogen uptake rates and thus an underestimate of new and regenerated production. In these studies, traditional nitrogen-15 techniques were found to underestimate new and regenerated production by up to 74 and 50 percent, respectively. Total DON turnover times, estimated from DON release resulting from both NH4+ and NO3(-) uptake, were 10 +/- 1, 18 +/- 14, and 4 days for oceanic, coastal, and estuarine sites, respectively

Otolith microchemical analyses of the strontium (Sr) and calcium (Ca) concentrations in the eels Anguilla japonica and A. anguilla caught in Tokyo Bay were undertaken to reconstruct the eels' migratory histories. A. japonica in the yellow stage (immature stage) were caught in a bay without any adjacent rivers or streams. A. anguilla was in the silver stage (early maturing stage), and the eel was confirmed to have just begun spawning migration to the open ocean from Tokyo Bay based on the otolith Sr:Ca ratios, which showed a typical catadromous life history with low Sr:Ca ratio values throughout the eel's life after recruitment. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicated the eels belonged to several general categories of migratory histories, including sea eels (average Sr:Ca ratio =6.0 x 10E-3) and estuarine eels (average Sr:Ca ratio 2.5 to 6.0 x 10E-3) based on the criteria reported previously in A. japonica. All eels had a certain freshwater life period, although the period was highly variable among fish. These results indicate that A. japonica has a flexible pattern of migration, with the ability to adapt to various habitats and salinities.

DDT is reductively dechlorinated to DDD and dehydrochlorinated to DDE; it has been thought that DDE is not degraded further in the environment. Laboratory experiments with DDE-containing marine sediments showed that DDE is dechlorinated to DDMU in both methanogenic and sulfidogenic microcosms and that DDD is dehydrochlorinated to DDMU three orders of magnitude more slowly. Thus, DDD does not appear to be an important precursor of the DDMU found in these sediments. These results imply that remediation decisions and risk assessments based on the recalcitrance of DDE in marine and estuarine sediments should be reevaluated