Lúcia Maria de Oliveira Gusmão

Diel and seasonal changes in the macrozooplankton community of a tropical estuary in Northeastern Brazil

Studies were carried out to assess the macrozooplankton small-scale temporal and spatial variability at three stations in three hours intervals, during 24 hours in July 1996 (rainy season) and December 1996 (dry season). A plankton net 300µm mesh size was hauled at surface during three minutes. Water samples for salinity, temperature, dissolved oxygen and pH were taken simultaneously with the zooplankton samples. Sixty-five macrozooplankton taxa were registered. Copepoda constituted the most common taxon and comprised 58% of the total zooplankton counts. Brachyuran zoeae, cirripedian larvae, Larvacea (Oikopleura dioica Fol, 1872), and Gastropoda veligers were abundant at some tidal cycles, mainly during the night. Species diversity average was 2.0 bits.ind-1. The mean density ranged from 23 ind.m-3 to 5,201 ind.m-3. The rainy season presented greater numerical abundance. A regular temporal zooplankton cycle was not observed. Instead, there was a large stochastic variation between samples.

Mesozooplankton of an impacted bay in North Eastern Brazil

Mesozooplankton abundance and distribution at Suape Bay, Pernambuco, was studied to assess the impacts caused by the construction of an internal port to increase the capacity of the Suape Port Complex. Zooplankton sampling was done at 3 stations during the dry (November-December/1997) and rainy (April-May/1998) seasons. A plankton net with 300 µm mesh size was used. Wet weight plankton biomass ranged from 44 mg.m-3 to 3,638 mg.m-3. Forty-five macrozooplankton taxa were registered. The most abundant was Copepoda. Among copepods, Acartia lilljeborgi, Parvocalanus crassirostris, Oithona hebes, Corycaeus (C.) speciosus and Temora turbinata were most frequent. Minimum abundance was 9 ind.m-3 and maximum was 2,532 ind.m-3. Average species diversity was 2.55 bits.ind-1. As a whole, Suape Bay has been under severe environmental stress and it seemed reasonable to assume that the recent modifications of the basin have resulted in changes in species composition and trophic structure, with an increase in marine influence.

Demersal zooplankton communities from tropical habitats in the southwestern Atlantic

Abstract Demersal zooplankton were captured with traps from a set of tropical coastal habitats (seagrass bed, coral reef, gravel, and sand bottoms) to allow comparisons among communities. Sampling was carried out during dry and rainy seasons in 2000 and 2001. Traps with and without light were placed at 18:00 and removed at 06:00 the next day for three consecutive days. Eighty-eight zooplankton taxa were identified. Copepoda was the most abundant group, outranking in relative abundance in seagrass and in sandy bottoms. Copepoda was mainly represented by Oithona oculata, Pseudodiaptomus acutus, and Acartia lilljeborgi. No significant differences were found among substrates (P=0.1464); however, differences were significant between light and dark traps communities (P=0.0410). The average density was 7113 (±3966) ind m−2 in the light and 4759 (±4825) ind m−2 in the dark. In the light traps, Amphipoda and O. oculata were more representative. Without light, the main group was Foraminifera (>40%). Cluster analysis presented two main groups, Itamaracá Island and Tamandaré Bay; light and dark traps formed separate groups within these location groups. The results allow us to assess the efficiency of the used traps in a set of habitats of the tropical coastal area and gives information on the preference of specific organism groups in one of the tested substrates.

Zooplankton from shrimp culture ponds in Northeastern Brazil

Zooplankton was examined in 14 commercial shrimp Litopenaeus vannamei ponds in tropical Brazil to assess their composition, determine their density, and indicate environmental quality. In each farm, two ponds and the water intake point were monitored in 2003. Sampling was made with a standard plankton net 50 micrometers mesh size. The zooplankton presented 40 taxa and was essentially composed of typical marine euryhaline species and suspensionfeeding forms. In all farms the dominant group was Copepoda with a total of 45%, followed by Protozoa (18%). The most abundant meroplankton were Polychaeta larvae, Gastropoda larvae, nauplii of Cirripedia and zoeae of Brachyura with large distribution in the region, sometimes dominating the community. Zooplankton abundance varied from 972+209 ind m -3 to 4,235 + 2,877 ind m -3 . In the studied marine shrimp culture ponds, copepods dominance were replaced by protozoan and rotifers as nutrient concentrations increased with the culture period, indicating that zooplankton trophic structure can be strongly affected by the occurrence of eutrophic conditions in shrimp ponds. The tendency of low species diversity is indicative of an unbalanced hypereuthrophic system decreasing the water quality and the cultured species. These results can be an important appointment to understand the effects of eutrophication in coastal plankton structure and its effects to marine aquatic food web.