Receiving coastal waters and estuaries are among the most nutrient-enriched environments on earth, and one of the symptoms of the resulting eutrophication is the proliferation of opportunistic, fast-growing marine seaweeds. Here, we used a widespread macroalga often involved in blooms, Ulva spp., to investigate how supply of nitrogen (N) and phosphorus (P), the two main potential growth-limiting nutrients, influence macroalgal growth in temperate and tropical coastal waters ranging from low- to high-nutrient supplies. We carried out N and P enrichment field experiments on Ulva spp. in seven coastal systems, with one of these systems represented by three different subestuaries, for a total of nine sites. We showed that rate of growth of Ulva spp. was directly correlated to annual dissolved inorganic nitrogen (DIN) concentrations, where growth increased with increasing DIN concentration. Internal N pools of macroalgal fronds were also linked to increased DIN supply, and algal growth rates were tightly coupled to these internal N pools. The increases in DIN appeared to be related to greater inputs of wastewater to these coastal waters as indicated by high δ15N signatures of the algae as DIN increased. N and P enrichment experiments showed that rate of macroalgal growth was controlled by supply of DIN where ambient DIN concentrations were low, and by P where DIN concentrations were higher, regardless of latitude or geographic setting. These results suggest that understanding the basis for macroalgal blooms, and management of these harmful phenomena, will require information as to nutrient sources, and actions to reduce supply of N and P in coastal waters concerned.

The feeding habits of Rioraja agassizii (syn. Raja agassizii) and Psammobatis extenta (syn. Psammobatis glansdissimilis) of the South-eastern Brazilian coast were studied by means of stomach content analysis. The samples were obtained on eight seasonal oceanographic cruises, carried out between October 1985 and July 1987. The importance of each food item was evaluated on the basis of the Index of Relative Importance and the feeding similarity by Percentage of Similarity. The results indicated that both species are benthic feeders, preying mainly on Crustacea, especially Amphipoda, Caridea and Brachyura. Teleostei were also important for R. agassizii. Seasonal variation of the diet seems to be associated with the availability of the prey, whose distribution and abundance are related to the dynamics of the water masses of the region. Juveniles and adults of P. extenta exploited the same resources while juveniles and adults of R. agassizii presented low diet similarity during most of the year. Caridea were an important food for all length classes of R. agassizii, while Amphipoda were for smaller specimens, and Teleostei for larger ones. The feeding overlap between the two species was higher during autumn 1986, winter 1986 and winter 1987.

A dual isotope approach was used to assess the relative importance of terrestrial vegetation detritus and other primary producers in the trophic web of Flamengo Sound (Ubatuba, SP), SE Brazil, surrounded by the Atlantic Rain Forest. Primary producers showed distinct d 13 C signatures and the observed values suggest that little terrestrial ðÀ29:4 AE 0:3‰Þ or bulk sediment organic matter ðÀ21:1 AE 1:3‰Þ enter the food web of the sound. Suspended particulate organic matter (POM, À18:6 AE 0:5‰Þ supports the bulk of the consumers, with some contribution by macroalgae ðÀ15:6 AE 1:8‰Þ. Consumers d 13 C values ranged from )17.4 to À12:7‰. At least three trophic levels were detectable in the food web. The d 15 N value of POM was 7:5 AE 1:0‰, while that of sediment and detritus was 6:4 AE 0:7‰. The d 15 N values of suspension feeding benthic invertebrates were 8.2-8:6‰, deposit feeders 8.3-10:2‰, and carnivores 10.7-13:2‰. Values for fishes were 9:4‰ for detritivore, 11.4-13:3‰ for benthic feeders, 12.4-13:3‰ for zooplanktivores, and 13:2‰ for piscivores/benthic invertebrate feeders. Squid mean value was 12:8 AE 0:5‰. There is a reasonable agreement between feeding habits information from the literature and d 15 N values from this study. In the sound, the first and second trophic steps seem to be about 1-3‰ higher than those of similar organisms studied in temperate waters and this may reflect an input of allochtonous anthropogenic nitrogen enriched in 15 N from human activities.

Com o objetivo de detectar grupos tróficos, foram analisadas amostras de conteúdos estomacais de sete espécies de peixes cartilaginosos. Os exemplares foram coletados no período de Outubro/85 a Julho/87 na plataforma interna de Ubatuba, SP, Brasil (da costa, até a isóbata de 50 m). A importância dos itens alimentares foi analisada através da freqüência numérica (FN) e da freqüência de ocorrência (FO). As espécies foram agrupadas em três grupos distintos: Piscívoros: Squalus cubensis; comedores de peixes e crustáceos bentônicos: Raja castelnaui, Raja cyclophora, Raja agassizi; comedores de invertebrados bentônicos: Psammobatis glansdissimilis, Rhinobatos horkelii, Zapteryx brevirostris.

The demersal fish community of the Channel and shelf of São Sebastião (SP), on the southeastern Brazilian coast, was investigated during the summer of 1994. The sampling was carried out usinga bottom otter trawl at 26 stations located between 8 m and 65 m in depth. Ninety-three species of 40 families were identified in the area. Sciaenids were the most prominent in number of species, abundance, and weight. Ctenosciaena gracilicirrhus, Paralonchurus, brasiliensis, and Cynoscion jamaicensis dominated in the catches. Cluster analysis showed three major groups of species and three groups of sites. The first group was composed of species found in the Channel and shallower areas of the inner shelf, the second of species associated with the inner shelf «50 m depth), and the third group of species fTom the outer shelf (> 50 m depth). Environrnental variables considered in Canonical Correspondence Analysis (CCA) explained 51 % of the variation in the species data. Bottom water temperature was the most important variable selected by CCA, accounting for 21% of the explainable variance. The results revealed that structure of the ichthyofauna was associated with water mass distribution. During the period studied, the area was occupied by the warm Coastal Water (CW), but cold South Atlantic Central Water (SACW) was detected over the bottom or the outer shelf, influencing the distribution and abundance ofthe main species.
A comunidade de peixes demersais do canal e plataforma de São Sebastião (SP), costa sudeste do Brasil, foi investigada no verão de 1994. A amostragem foi realizada com rede de arrasto de fundo, em 26 estações localizadas entre 8 t' 65 m de profundidade. Foram identificadas 93 espécies pertencentes a 40 famílias. Os cienídeos foram os mais representativos em número de espécies, abundância e peso, sendo Ctenosciaena gracilicirrhus, Paralonchurus brasiliensis e Cynoscion jamaicensis as espécies dominantes. A análise de agrupamento revelou três grandes grupos de espécies e três grupos de estações. O primeiro grupo caracterizou-se pela presença de espécies com ocorrência no canal e regiões costeiras da plataforma interna; o segundo por espécies associadas à plataforma interna >50 m de profundidade) e o terceiro grupo por espécies relacionadas à plataforma externa (>50 m). As variáveis ambientais selecionadas pela CCA explicaram 51 % da variação dos dados das espécies, sendo a temperatura da água de fundo a mais importante, representando 21% da variância. Verificou-se a importância da distribuição das massas d'água na estruturação da comunidade de peixes demersais. Durante o período de amostragem a área foi ocupada pela massa d'água quente da Água Costeira (AC). No entanto, a presença da Água Central do Atlântico Sul (ACAS), mais fria, foi detectada na camada de fundo da plataforma externa, influenciando a distribuição e abundância das espécies dominantes