How do cold water biota arrive in a tropical bay near Rio de Janeiro, Brazil?

Previous ecological studies on foraminifera and ostracoda from the tropical Sepetiba Bay, located in the southern part of the State of Rio de Janeiro, Brazil, have noted the presence in this area of some cool water taxons typical of the Argentine continental platform. These studies have proposed that parcels of these temperate waters with their associated biological indicators are advected northward along the platform, penetrating into some tropical entrances of the southeast coast of Brazil. In the present study, ecological data (foraminifera, ostracoda and microbivalves), are used together with information obtained by satellite tracked drifting buoys and digital thermal imagery obtained from NOAA satellites to indicate the path taken by these high latitude species along the southern Brazilian coast to arrive in the Sepetiba Bay, near the city of Rio de Janeiro. Our general conclusion is that biotic elements native to the colder, less saline marine waters seen to the south of Brazil have been and are being advected northward along the inner part of the continental platform to about 22 degrees S. Water parcels containing this biota may, in a sporadic fashion, enter into the tropical Sepetiba Bay. The passage of meteorological fronts through the region is considered to be an important if not the principal mechanism for the sporadic entry of the cool water into the Southern Coastal Entrance of the State of Rio de Janeiro. (C) 1998 Elsevier B.V.s Ltd. All rights reserved.

Temporal and Spatial Variability of Mesozooplankton in a Shallow Sub-Tropical Bay: Influence of Top-Down Control

Quantifying the relationship between mesozooplankton and water quality parameters identifies the factors that structure the mesozooplankton community and can be used to generate hypotheses regarding the mechanisms that control the mesozooplankton population and potentially the trophic network. To investigate this relationship, mesozooplankton and water quality data were collected in Florida Bay from 1994 to 2004. Three key characteristics were found in the mesozooplankton community structure: (1) there are significant differences between the four sub-regions of Florida Bay; (2) there is a break in May of 1997 with significant differences before and after this date; and (3) there is a positive correlation between mesozooplankton abundance and salinity. The latter two characteristics are closely correlated with predator abundance, indicating the importance of top-down control. Hypersaline periods appear to provide a refuge from predators, allowing mesozooplankton to increase in abundance despite the increased physiological stress.

Seasonal contrasts in abundance and reproductive parameters of Penilia avirostris (Cladocera, Ctenopoda) in a coastal subtropical area

We studied the population dynamics and the reproductive biology of Penilia avirostris during three consecutive years on the inner shelf off Ubatuba, Brazil. Penilia avirostris individuals and its eggs and embryos were counted, measured, and classified into stages. The species occurred throughout the studied period, in a wide temperature range (14.8-28.2A degrees C). Cladoceran densities were usually higher (> 2,000 ind m(-3)) in warm seasons, when the water column was stratified as a consequence of bottom intrusions of the cold- and nutrient-rich South Atlantic Central Water. Juveniles, non-reproducing females, and parthenogenic females were the dominant developmental stages. Males and gamogenic females were rare and only occurred when females reached peak abundances. This suggests that in tropical and subtropical coastal seas gamogenesis in P. avirostris is not as common as in temperate seas, but may play a significant role in the density-dependent control of the population preceding unfavourable periods.

Life cycle and reproductive traits of marine podonids (Cladocera, Onychopoda) in a coastal subtropical area

We studied the temporal distribution and reproductive biology of marine podonids during two consecutive years off Ubatuba, southeast coast of Brazil. Podonid specimens and their eggs and embryos were counted, measured and classified into categories. Pseudevadne tergestina was the most abundant species, and was more abundant in surface layers, in warm seasons, when the water column was stratified because of bottom intrusions of the cold and nutrient-rich South Atlantic Central Water (SACW) onto the inner shelf. Evadne spinifera had a similar temporal and vertical distribution, but with lower abundance and frequency. Pleopis schmackeri did not show a clear seasonal distribution, but preferred bottom layers. Pleopis polyphemoides and Podon intermedius occurred in low abundances, and only under SACW influence. Parthenogenetic females were dominant among all podonid species. Gamogenetic females of P. polyphemoides and P. intermedius were observed, but males of neither species occurred. This suggests that in tropical and subtropical regions, P. tergestina, E. spinifera and P. schmackeri reproduce through parthenogenesis during most of the year.

Population structure of the lancelet Branchiostoma caribaeum (Cephalochordata: Branchiostomidae) in the Baia de Guanabara, Rio de Janeiro, southeastern Brazil

Population structure of the lancelet Branchiostoma caribaeum Sandevall, 1853 was studied in four surveys, corresponding to austral seasons, in a tropical bay, southeast of Brazil. Abundance was higher in the spring and was positively correlated to coarse sediments, limiting its occurrence to some sectors of the sampling area. Body length and biomass differed seasonally but not between sexes. Sexually mature individuals occurred in all seasons, suggesting continuous breeding that is typical of tropical species. Variation in the frequency of small specimens indicates temporal differences in the intensity of breeding. The body length of recruits differed from other population of lancelets and the small length which B. caribaeum attained sexual maturity in Guanabara Bay may be related to local environmental stress or the great availability of food.

Taxonomic sufficiency of polychaete taxocenes for estuary monitoring

The polychaetes assemblage structure was used in order to investigate taxonomic sufficiency in a heavily polluted tropical bay. Species abundance was aggregated into progressively higher taxa matrices (genus, family, order) and was analyzed using univariate and multivariate techniques. Polychaetes distribution in Guanabara Bay (GB) was in accordance with a pollution gradient, probably ruled by the organic enrichment, consequent effects of hypoxia and altered redox conditions coupled with prevailing patterns of circulation. Within the sectors of GB, an increasing gradient in species richness and occurrence was observed, ranging from the azoic and impoverished stations in the inner sector to a well-structured community in terms of species composition and abundance inhabiting the outer sector. Multivariate statistical analysis showed similar results when species were aggregated into genera and families, while greater difference occurred at coarser taxonomic identification (order). The literature about taxonomic sufficiency has demonstrated that faunal patterns at different taxonomic levels tend to become similar with increased pollution. In GB, an analysis carried out solely at family level is perfectly adequate to describe the environmental gradient, considered a useful tool for a quick environmental assessment. (C) 2011 Elsevier Ltd. All rights reserved.

Surface freshwater from Bay of Bengal runoff and Indonesian Throughflow in the Tropical Indian Ocean

According to recent estimates, the annual total continental runoff into the Bay of Bengal (BoB) is about 2950 km 3, which is more than half that into the entire tropical Indian Ocean (IO). Here we use climatological observations to trace the seasonal pathways of near surface freshwater from BoB runoff and Indonesian Throughflow (ITF) by removing the net contribution from precipitation minus evaporation. North of 20 degrees S, the amount of freshwater from BoB runoff and ITF changes with season in a manner consistent with surface currents from drifters. BoB runoff reaches remote regions of the Arabian Sea; it also crosses the equator in the east to join the ITF. This freshwater subsequently flows west across the southern tropical IO in the South Equatorial Current.

Influence of the tidal and rainfall cycles on the population structure and density of Mesacanthion hirsutum gerlach (nematoda, thoracostomopsidae) on a tropical sandy beach (Tamandaré Bay, Pernambuco, Brazil)

A estrutura populacional (machos, fêmeas e juvenis) e densidade de Mesacanthion hirsutum Gerlach foram estudadas durante as marés (baixa, enchente, alta e vazante) de dois ciclos de maré consecutivos, em quatro meses diferentes do ano (Maio, Julho, Setembro e Novembro). As variações de densidade de Mesacanthion hirsutum mostraram associação com o ciclo de chuvas, com densidades mais baixas durante Julho e Setembro e significativamente maiores em Maio e Novembro. A estrutura populacional constituiu-se em sua maior parte por juvenis indicando uma reprodução continua durante todo o período de estudo. Não foram encontradas diferenças significativas entre os períodos claros e escuros do dia, contudo maiores densidades foram detectadas durante as marés altas e vazantes demonstrando que a espécie pode estar se dispersando através da coluna d'água e/ou migrando dentro do sedimento.

CAPTURE FISHERY IN NORTHERN TODOS OS SANTOS BAY, TROPICAL SOUTHWESTERN ATLANTIC, BRAZIL

Information on marine and estuarine capture fishery activity in northern Todos os Santos Bay, northeastern Brazil, based on daily data collected between September 2003 and June 2005 is presented. Small-scale artisanal fishery in this area includes the use of traditional vessels both non-motorized and motorized for locomotion, being carried out mainly by canoe or on foot, and involves many different kinds of gear, including gillnet, hook and line, seine nets, and traps. A total of 113 taxa were grouped into 77 resources, including 88 fish, 10 crustaceans, and 15 mollusks. Data on nominal catches of fish, crustaceans and mollusks are presented by month and location. A total of 345.2 tonnes of fishery resources were produced (285.4 tonnes of fish, 39.2 tonnes of fresh invertebrates, and 20.6 tonnes of processed invertebrates). Temporal variation in the fish catch was associated with the life cycle of the species or with the hydrographic conditions. The first-sale value of this catch amounted to around US$ 615,000.00, fishes representing 71.3% of it. A table of the average price of each fishery resource is presented. The results produced in this study may be considered a reference for future monitoring programs of fishery resources in the area.

Climatic Controls on Phytoplankton Biomass in a Sub-tropical Estuary, Florida Bay, USA

The extraction of climatic signals from time series of biogeochemical data is further complicated in estuarine regions because of the dynamic interaction of land, ocean, and atmosphere. We explored the behavior of potential global and regional climatic stressors to isolate specific shifts or trends, which could have a forcing role on the behavior of biogeochemical descriptors of water quality and phytoplankton biomass from Florida Bay, as an example of a sub-tropical estuary. We performed statistical analysis and subdivided the bay into six zones having unique biogeochemical characteristics. Significant shifts in the drivers were identified in all the chlorophyll a time series. Chlorophyll a concentrations closely follow global forcing and display a generalized declining trend on which seasonal oscillations are superimposed, and it is only interrupted by events of sudden increase triggered by storms which are followed by a relatively rapid return to pre-event conditions trailing again the long-term trend.

New particle formation and growth at a remote, sub-tropical coastal location

A month-long intensive measurement campaign was conducted in March/April 2007 at Agnes Water, a remote coastal site just south of the Great Barrier Reef on the east coast of Australia. Particle and ion size distributions were continuously measured during the campaign. Coastal nucleation events were observed in clean, marine air masses coming from the south-east on 65% of the days. The events usually began at ~10:00 local time and lasted for 1-4 hrs. They were characterised by the appearance of a nucleation mode with a peak diameter of ~10 nm. The freshly nucleated particles grew within 1-4 hrs up to sizes of 20-50 nm. The events occurred when solar intensity was high (~1000 W m-2) and RH was low (~60%). Interestingly, the events were not related to tide height. The volatile and hygroscopic properties of freshly nucleated particles (17-22.5 nm), simultaneously measured with a volatility-hygroscopicity-tandem differential mobility analyser (VH-TDMA), were used to infer chemical composition. The majority of the volume of these particles was attributed to internally mixed sulphate and organic components. After ruling out coagulation as a source of significant particle growth, we conclude that the condensation of sulphate and/or organic vapours was most likely responsible for driving particle growth during the nucleation events. We cannot make any direct conclusions regarding the chemical species that participated in the initial particle nucleation. However, we suggest that nucleation may have resulted from the photo-oxidation products of unknown sulphur or organic vapours emitted from the waters of Hervey Bay, or from the formation of DMS-derived sulphate clusters over the open ocean that were activated to observable particles by condensable vapours emitted from the nutrient rich waters around Fraser Island or Hervey Bay. Furthermore, a unique and particularly strong nucleation event was observed during northerly wind. The event began early one morning (08:00) and lasted almost the entire day resulting in the production of a large number of ~80 nm particles (average modal concentration during the event was 3200 cm-3). The Great Barrier Reef was the most likely source of precursor vapours responsible for this event.

Cyclone-induced mixing does not cool SST in the post-monsoon north Bay of Bengal

High-resolution data from the TRMM satellite shows that sea surface temperature (SST) cools by 3 degrees C under the tracks of pre-monsoon tropical cyclones in the north Indian Ocean. However, even the strongest post-monsoon cyclones do not cool the open north Bay of Bengal. In this region, a shallow layer of freshwater from river runoff and monsoon rain caps a deep warm layer. Therefore, storm-induced mixing is not deep, and it entrains warm subsurface water. It is possible that the hydrography of the post-monsoon north Bay favours intense cyclones.