Retention and leaching losses of atmospherically-derived nitrogen in the aggrading coastal watershed of Waquoit Bay,MA

Extensive areas of the eastern United States are being exposed to elevated levels of nitrogen in precipitation, with levels of inorganic N in wet deposition ranging from 5 to over 20 times preindustrial, background levels. This increase in N loading to the terrestrial system, coupled with changes in land use in coastal regions in particular, has dramatically increased the level of nutrient loading from watersheds to the point that coastal waters are today among the most intensely fertilized ecosystems on earth. Studies in upland, aggrading forests have generally found that precipitation N inputs are efficiently sequestered in forest biomass and soil organic matter. However, acidic soils, sandy, porous parent substrates, and chronic inputs of salt spray common to coastal watersheds may all reduce the potential for N sequestration by the terrestrial community.We assessed the role of coastal forests in the long-term storage and retention of atmospherically-derived N in the watersheds of Waquoit Bay, MA, an increasingly eutrophic estuary on Cape Cod, by measuring precipitation inputs, storage, and lysimeter outputs below the rooting zone in a chronosequence of sites released from agriculture at different times. Calculated annual retention efficiencies were relatively low for an N-limited, aggrading forest (40–62%), and leaching losses did not vary with site age from young pine stands to mature beech forests. Nearly all nitrogen input was retained during summer months except in months with very high rainfall events. Nitrogen was released during the dormant-season in proportion to water flux through the forest floor. The composition of lysimeter output was 76% DON, 11% NO ₃ ^– , and 13% NH ₄ ^– . Total water flux and infiltration appear to be more important determinants of N retention in this sandy, coastal site than in more upland forest ecosystems; sandy systems may inherently have a low N retention efficiency.     

Organic matter composition in coastal sediments at Terra Nova Bay (Ross Sea) during summer 1995

We illustrate the spatial and vertical distribution of sediment phytopigments and organic matter biochemical composition at Terra Nova Bay (Ross Sea) during summer 1995. Coastal sediments displayed high phytopigments concentrations associated with huge amounts of labile organic matter largely dominated by proteins. This result was opposite to previous observations in the same area. Such comparison suggested that whilst organic matter quantity in the sediments depended upon the vertical input from the water column, temporal changes in its biochemical composition were related to benthic processes. As considerably high concentrations of biopolymeric organic carbon were found even at 6-cm depth and according to the “loss type” functioning of the coastal waters of the Ross Sea, we stress the summer time occurrence in coastal sediments of an important organic matter burial. Accepted: 24 October 1999     

Diversity of bacterial communities related to the nitrogen cycle in a coastal tropical bay

A culture-independent molecular phylogenetic analysis was carried out to study for the first time the diversity of bacterial ammonia monooxygenase subunit A (amoA) and nitrogenase reductase subunit H (nifH) genes from Urca inlet at Guanabara Bay in Rio de Janeiro, Brazil. Most bacterial amoA and nifH sequences exhibited identities of less than 95% to those in the GenBank database revealing that novel ammonia-oxidizing bacteria and nitrogen-fixing microorganisms may exist in this tropical marine environment. The observation of a large number of clones related to uncultured bacteria also indicates the necessity to describe these microorganisms and to develop new cultivation methodologies.     

Diatoms and dinoflagellates in Terra Nova Bay (Ross Sea-Antarctica) during austral summer 1990

During January/February 1990 the floristic composition and biomass of diatoms and dinoflagellates in Terra Nova Bay (Ross Sea) were investigated. The study area included eight stations, seven of which were inshore and one offshore. Of the 94 taxa identified, 58 were diatoms and 34 were dinoflagellates. Cell densities were higher in surface layers and particularly at two stations, one located at the centre of the bay, and the other to the south of the Terra Nova station. While density data showed that the diatoms predominated over the dinoflagellates and over Phaeocystis sp., the biomass values were largely made up of the dinoflagellates contribution.     

The development of sessile epifaunal communities in Kylesalia,Kilkieran bay (west coast of Ireland)

Test panels, which were suspended horizontally at three sites in a shallow inlet on the west coast of Ireland, were sampled monthly over a period of one year to investigate the development of epifaunal communities. In addition, the current regime and sedimentation at these sites were measured. The deposited materials, of high organic value, may enhance the food supply to the sessile organisms through resuspension. Heavy deposition at one site interrupted the study. At the other two sites, however, the experiment was not affected. At one site, initial settlement by colonial bryozoans, followed by solitary ascidians, was noted on the panels over the period studied. In the competition for space, the dense aggregations during settlement, the relative large size, and the rapid growth of these solitary animals may occlude the colonization by colonial bryozoan mats underneath. At the other site, a more diversified community with co-existence of many sedentary polychaete and colonial bryozoan species was recorded on the panels. The continuing availability of free space on the panels suggests that the development of sessile communities at this site may be hindered by the relatively slow current flow and heavy deposition and resuspension. Whilst differences in community development were observed on the panels at these two sites, it would be difficult, through such a short study period, to ascertain whether stable climax states had been reached.     

Evidence of heterotrophic prokaryotic activity limitation by nitrogen in the Western Arctic Ocean during summer

Global warming in the Arctic Ocean may result in changes to the stock and dynamics of nutrients that drive the activity of heterotrophic prokaryotes, a key component of the microbial food web. We performed 14 enrichment experiments during summer in the Beaufort and Chukchi Seas (Western Arctic Ocean), with C (acetate and/or glucose), N (nitrate and/or ammonium) and P (phosphate) amendments. In 8 out of 11 experiments performed with surface waters, prokaryotic heterotrophic production was limited by N, either alone (5 experiments) or in co-limitation with C (3 experiments). This contrasted with the experiments performed using waters from the chlorophyll maxima, where N was never limiting. Diversity analyses (DNA- and RNA-based fingerprinting) suggest that limitation was not restricted to specific operational taxonomic units but common to the different groups. This is the first report of N limitation of prokaryotic heterotrophic production in Arctic surface waters. This control by N may gain importance in future scenarios of higher productivity in the area.     

Temporal and spatial variation in coastal macrobenthic community structure,hanö bay (southern Baltic)

Quantitative (0.1-m²) samples of benthic macrofauna were taken at three depths (5, 10, 17 m) off the eastern coast of Scania, southern Baltic, in the period April 1974 to August 1978. Altogether 20 sampling cruises were made. Spatial and temporal species composition, abundance and biomass were compared. The number of species increased significantly with increasing depth. Zonation of the species was due to their zoogeographical origin and capacity to withstand exposure. Abundance was highest at 5 m depth whereas biomass increased with depth due to the dominance of large bivalves. Variation in abundance within years was large at all three depths and connected with reproductive recruitment for all species except Bathyporeia pilosa Lindström which migrated towards the shore in summer.     

Increasing nitrogen limitation during summer in the List Tidal Basin (Northern Wadden Sea)

The European Wadden Sea is characterized by high nutrient loads and turbid waters. Riverine nutrient input showed a gradual decrease since the mid 1980s. In the List Tidal Basin (Northern Wadden Sea) the frequency of low NO₃ values in summer has increased and decreasing mean annual suspended matter concentrations indicate an increasing underwater irradiance. We used an approach developed by Cloern (Aquat Ecol 33:3–16, 1999) to analyze resource limitation of nitrogen (DIN) and underwater irradiance for phytoplankton growth in the List Tidal Basin between 1985 and 2005. Comparing our results to other studies suggests that the List Tidal Basin is one of the most nitrogen sensitive areas of the European Wadden Sea. In 2005, phytoplankton growth was light limited from January to May and in November and December, co-limited by both resources in June, July and October, and nitrogen limited in August and September. Comparing phytoplankton growth limitation in the periods 1985–1991 and 1999–2005, the duration of nitrogen limitation during summer is significantly longer in the second period (2.1 ± 0.9 months) than in the first (0.7 ± 0.5). Moreover, light limitation in September and October has decreased in the second period. A decreasing phytoplankton growth during summer is in line with former studies from the List Tidal Basin, which showed that summer chlorophyll concentrations have decreased since the mid 1980s. We suggest that nowadays less food is available for higher pelagic and benthic trophic levels due an increased nitrogen limitation during summer.     

Microzooplankton herbivory and bacterivory in Newfoundland coastal waters during spring, summer and winter

Grazing by microzooplankton on autotrophic and heterotrophicpicoplankton as well as >0.7 µm phytoplankton (as measuredby chlorophyll a) was quantified during July, August, October,January and April in the surface layer of Logy Bay, Newfoundland(47°38'14'N, 52°39'36'W). Rates of growth and grazingmortality of bacteria, Synechococcus and >0.7 µm phytoplanktonwere measured using the sea water dilution technique. Microzooplanktoningested 83–184, 96–366 and 64–118% of bacterial,Synechococcus and >0.7 µm phytoplankton daily potentialproduction, respectively and 34–111, 25–30 and 16–131%of bacterial, Synechococcus and >0.7 µm phytoplanktonstanding stocks, respectively. The trends in prey net growthrates followed the seasonal cycles of prey biomass, suggestingthat microzooplankton are important grazers in Newfoundlandcoastal waters. Ingestion was lowest during January and October(~2 µg C l^–1 day^–1) and highest in August(~20 µg C l^–1 day^–1). Aside from April when>0.7 µm phytoplankton represented the majority (~80%)of carbon ingested, bacterioplankton and <1 µm phytoplanktonrepresented most of the carbon ingested (~40–100%). Althoughmicrozooplankton have here-to-fore been unrecognized as an importantgrazer population in Newfoundland coastal waters, these resultssuggest that they play an important role in carbon flow withinthe pelagic food web, even at low temperatures in Logy Bay.     

Mesozooplankton community in the Bay of Bengal (India): spatial variability during the summer monsoon

This study addresses the spatial variability in mesozooplankton biomass and composition in the Central and Western Bay of Bengal (India) during the summer monsoon season of 2001. Perennially warmer sea surface temperatures (>28°C), stratified top layer (sea surface salinity, 28–33 psu), high turbidity, and low nutrient concentrations due to weak/null upwelling and light limitation make the Bay of Bengal a region of low primary productivity. Despite this, mesozooplankton biomass values, i.e. 2.9–104 mg C m⁻³ in the Central Bay and 1.3–31 mg C m⁻³ in the Western Bay, observed in the mixed layer (2–51 m) during the summer monsoon were in the same range as reported from the more productive Arabian Sea. Mesozooplankton biomass was five times and density 18 times greater at stations with signatures of cold-core eddies, causing a higher spatial heterogeneity in zooplankton distribution. Among the 27 taxonomic groups recorded during the season, Copepoda was the most abundant group in all samples followed by Chaetognatha. The dominant order of Copepoda, Calanoida, was represented by 132 species in a total of 163 species recorded. Oncaea venusta was the key copepod species in the Bay. In the Central Bay, the predominant copepod species were carnivorous/omnivorous vis-a-vis mostly herbivores in the Western Bay. Pleuromamma indica increased to its maximum abundance at 18°N in the Central Bay, coinciding with the lowest dissolved oxygen concentrations. The Central Bay had higher mesozooplankton biomass, copepod species richness and diversity than in the Western Bay. Although zooplankton biomass and densities were greater at the eddy stations, correlation between zooplankton and chl a was not statistically significant. It appears that the grazer mesozooplankton rapidly utilize the enhanced phytoplankton production in cold-core eddies.     

Diatoms of the Puck Bay coastal shallows (Poland, Southern Baltic)

In the study area 150 diatom taxa were identified, including several varieties. The characteristic feature of the community is the strong predominance of several epipsammic diatom species of which Achnanthes delicatula, Fragilaria construens var. venter, Navicula cryptolyra , and Opephora olsenii are the most abundant. The predominating taxa are autochthonous in the study area and their percent content ranges from 70 to 90%. In the sediments studied there was also a large group of species which are typical of the Puck Bay interior. They are usually represented by several specimens showing various degrees of destruction. Only few of them attain in the study area considerable percent contents e.g. Achnanthes lemmermanni, Amphora acutiuscula, Cocconeis scutellum, Diploneis interrupta, Navicula rhynchocephala, N. perminuta, Nitzschia frustulum and N. nana. Numerous taxa reported in the paper are recorded in the study area for the first time.     

Species composition and seasonal variations of ichthyoplankton of the coastal zone of Vostok Bay (Peter the great bay,sea of Japan) collected at light stations

We summarize the results of a study of the taxonomic composition and seasonal variations of ichthyoplankton in Vostok Bay. Samples were collected during 2003–2008 at a stationary light station located on the mooring module of the experimental biological station Vostok (Institute of Marine Biology). Within the observation period, larval and juvenile fish of 67 species belonging to 11 orders and 30 families were found in 412 samples. The seasonal dynamics of species composition of ichthyoplankton were examined over the period from March to November. The number of species in the samples changed from 40–36 in April–May, respectively, to 6 species in October. The contribution of resident species and southern migrants to the ichthyoplankton samples was estimated. The light station sampling has proven to be most effective in studying the species diversity of the ichthyofauna in Vostok Bay. Using light station sampling, 18 fish species were found that were not recorded using other sampling techniques.     

Distribution of loliginid squids in a eutrophicated tropical coastal bay

Guanabara Bay is one of the most polluted bays in Brazil, although it supports some fisheries resources, among which are three species of loliginid squids: Lolliguncula brevis, Doryteuthis plei, and Doryteuthis sanpaulensis. This study aimed to assess the temporal and spatial variations of squids in the bay, relating their abundance variation to local environmental factors. We also aimed to characterize the population structure of squids, in order to establish their degree of occupancy in this estuarine system. Ten fortnightly hauls were carried out (two per area) from July 2005 to June 2007. Squids were identified, measured, weighed, sexed and classified according to maturity stage. The spatial distribution of the three species was not uniform; most individuals were found near the mouth of the bay. Abundances were significantly different among seasons due to the presence of SACW (South Atlantic Central Water) during the spring–summer season. Most of the populations of the three species consist of juveniles, and most adult Doryteuthis were also immature, which reinforces the role of Guanabara Bay as a nursery ground for loliginid squids. Concerning the degree of occupancy of squids in Guanabara Bay, L. brevis is considered an estuarine resident, D. plei uses the estuarine system as a nursery area for feeding and growth, and juveniles of D. sanpaulensis enter the bay with the flood tide to feed, generally following the SACW intrusion. This is the first study on squids in this estuarine system, which despite the high degree of environmental impact is shown to be an important area for the loliginid species.     

Seaweed Alaria esculenta as a biomonitor species of metal contamination in Aughinish Bay (Ireland)

The concentrations of ten metals (As, Cd, Cu, Fe, Hg, K, Na, Pb, Sn and Zn) were monitored in coastal seawater and biomass of the seaweed Alaria esculenta from Aughinish Bay on the West coast of Ireland during March–June 2014 in order to study their temporal variations and assimilation efficiencies and to assess the ecological quality of these ecosystems. Seawater and A. esculenta showed significant temporal variations in their metal concentrations during March–June 2014 and A. esculenta accumulated more efficiently Fe and Zn, but showed low sensitivity to Na and K. On the other hand, A. esculenta showed no active detoxication mechanisms for Cd and Pb, but no saturation point was observed during this work to any metal. Considering metal concentrations bioaccumulated by A. esculenta, the Irish coast of Aughinish Bay was always ecologically classified as “Class I – Unpolluted” during March–June 2014. The significant correlations between seawater and A. esculenta obtained to all metals proved that this seaweed species: (i) is a suitable biomonitor of metal contamination in Irish coasts; (ii) it can be included in the European Environmental Specimen Banks and (iii) it can be used in European Real-Time Environmental Monitoring Networks.