Estrutura e diversidade funcional de Copepoda em dois estuários tropicais

Abstract

This study characterized the community of Copepods as the structure and variation of functional diversity along the saline gradient in two estuaries of northeastern Brazil, Mamanguape (6º43'02‖ S; 35º67'46‖ W) and North Paraiba (6º57 '30' 'S; 34º51'30' 'W), in different periods: dry (November / 2013) and rain (July / 2014). Samples were collected in the amount-downstream direction, at high tide, full moon in four saline zones (Z1, Z2, Z3 and Z4), with three replicates at each sampling site of each of the saline areas, except the Z4 area of the North Paraiba estuary (CP), which took place in three replicas on each side of the island of Restinga. Samples collected with a 68 μm mesh organisms were screened and identified to the specific possible taxonomic level, proceeding to count them. In total, they identified 22 species, only being Notodiaptomus iheringi and Microcyclops anceps typical of freshwater areas, present only in the estuary of the Mamanguape, while Acartia tonsa and Paracalanus campaneri exclusive to North Paraiba estuary. The other species/genera are typical of estuarine-coastal ocean environments. In both estuaries, the highest density of organisms was observed during the rainy season, in the estuary of North Paraiba in Z2 and Z3 in the estuary of the Mamanguape. In the estuary of North Paraiba Oithona brevicornis had the highest density in the rainy season in areas Z2 (27 DIN / L), Z3 (24 DIN / L) and Z4 (12 DIN / L). The estuary of the Mamanguape O. brevicornis presented its highest density in the rainy season, registering 52 ind / L Z3 zone. During the dry period the input was observed in coastal-pelagic species toward upstream, as in the case of Oithona oswaldocruzi species which showed the highest densities in the Z1 zones (19DIN / L) Z2 (21DIN / L) and Z3 (25 DIN / L) in the estuary of Mamanguape, while in the rainy season the highest density was recorded in the zone Z3 (21 ind / L). In the estuary of North Paraiba, O. oswaldocruzi reached the value of 38 ind / L Z2 in the rainy season. For both estuaries, the largest biomass (ug / L) was recorded for O. brevicornis and O. oswaldocruzi during the rainy season. considering environmental data, dissolved inorganic nitrogen values (DIN) ranged from 23:54μg / L (Z4 - rain) to 460.98 μg / L (Z4) at the estuary of the Mamanguape whereas at the North Paraiba estuary it ranged from 434.30 μg / L (Z4) to 4139.54 μg / L (Z3) in the dry season, whereas in the rainy season variation was from 991.81 μg / L (Z4) to 4037.4 μg / L (Z3); total phosphorus (Pt) showed higher values in the North Paraíba (153.88 μg / L to 754.44 μg / L) compared to Mamanguape (63.33 μg / L to 284.44 μg / L); orthophosphate (ORP) ranged from 45 to 87 μg / L in the estuary of the Mamanguape and 57-191 μg / L in the North Paraiba estuary; reactive soluble phosphorus (SRP) had been steepest in North Paraiba, ranging from 68.55μg / L to 639.11 μg / L. Shannon-Wiener Analysis of Diversity presented the highest values in the Z4 in both estuaries, and the estuary of the Mamanguape (H '= 2.8 - drought) higher than in the estuary of North Paraiba (H' = 2.5 - rainy season). The results of PERMANOVA showed that there is no significant interaction between the density of mesozooplankton with the sampled points (Pseudo-F = 1.2326; P = 0.293), the collection periods (Pseudo-F = 3.4829; P = 0.026) and estuaries (Pseudo-F = 4.2619, P = 0.058), with only significant differences between the zones (olig, poly P = 0.004; olig, euha P = 0.016). As to functional diversity in both estuaries, functional richness index showed low values. In the North Paraiba estuary the highest values were recorded during the dry season in Z2, Z3 and Z4, while in Mamanguape the highest value was recorded in the Z3 in the dry season. The functional evenness index showed no significant differences by concentrating the highest value in the dry season in the estuary of the Mamanguape, and the lowest value observed in the dry season in the estuary of North Paraiba (Z2). The functional divergence rates were higher during the rainy season in both estuaries, but no major changes. The functional dispersion rates were low in both estuaries, but were more representative during the dry season. The study proved the existence of differences in copepod diversity along the salt gradient of both estuaries.