Abstract
Zooplankton is an important component to understand oceanographic dynamics, they are considered good indicators of environmental variability, since most species are short-lived they can be tight coupling of climate and population dynamics, and some taxa are sensitive to variables such as temperature, quality and quantity of food, oxygenation and stratification. In the Colombian Caribbean two oceanographic cruises were carried out, in order to characterize and analyze the biodiversity of the continental margin, for the periods May-June 2008 and November-December 2009. The objective of this study was to determine which oceanographic variable was the most important in the distribution of zooplankton in the oceanic waters, and how the variables structure the community. In each cruise, zooplankton samples were obtained by vertical hauls with a 1 m2 diameter conical net (200 μm mesh size). The zooplankton community structure was studied by automated image analysis (ZooImage), which combined with abundance data, allowed to calculate the slope of size spectrum, and diversity indexes of taxa and sizes. The environmental variables included temperature, salinity, oxygen and chlorophyll a of the water column, and were used to calculate the stratification with the Brunt-Vaiisala frequency; this information was complemented by satellite images of temperature, surface chlorophyll, geostrophic currents and sea level, obtained from MODIS and AQUA products. The association between environmental variables and the zooplankton community structure was determined using Spearman’s correlation ranges with the Bioenv routine and a stepwise regression model, and Principal component analysis (PCA). Our results showed spatial and temporal patterns in the oceanographic conditions of the study area, such as upwelling in the Northeast region, strong stratification in the Southwest, and mesoscale activity. The abundance of zooplankton exhibited differences between the two climatic seasons and zones. Temporal differences were also evident in the size and diversity of taxa (ANOVA 2-way p <0.05). These changes were related to the moderate upwelling and the activity of mesoscale eddies. Cyclonic and anticyclonic eddies of variable size can either transport or retain zooplankton over cross-shelf and oceanic areas, thus modifying the taxonomic structure of the community. According to the Bioenv analysis, the main variables that explained the abundance and composition of zooplankton were sea level and chlorophyll a (Spearman correlation = 0.49). The stepwise regression showed that stratification, oxygen and chlorophyll a were the most important predictors of zooplankton abundance and size. Rev. Biol. Trop. 66(2): 688-708. Epub 2018 June 01.
Highlights
Zooplankton are considered useful indicators of the impact of climate variability in the ocean environment, because they are composed mainly of short-lived species that respond rapidly to changes in their habitats, and reflect the responses of the entire marine ecosystem (Beaugrand, Reid, Ibanez, Lindley, & Edwards, 2002; Richardson & Schoeman, 2004)
We looked at the temperature at 10 m depth and estimated the mixed layer depth (MLD) by considering the density gradient and the first higher value as the base of the MLD
The weakening trend in Trade Winds and dependent local variables are largely explained by altering the Intertropical Convergence Zone (ITCZ) and North Atlantic oscillation (NAO)
Summary
Zooplankton are considered useful indicators of the impact of climate variability in the ocean environment, because they are composed mainly of short-lived species that respond rapidly to changes in their habitats, and reflect the responses of the entire marine ecosystem (Beaugrand, Reid, Ibanez, Lindley, & Edwards, 2002; Richardson & Schoeman, 2004). There have been few studies of the effects of climate variation on oceanographic processes, and the consequences for plankton dynamics and structure in the oceanic waters in the Caribbean. Two expeditions in the Caribbean and adjacent waters described the horizontal and vertical distribution of zooplankton species related to water masses near Colombia (Park, 1970; Michele & Foyo, 1976). These studies reported the greatest abundance in the Tropical Surface Water (0 - 50 m) and Subtropical Underwater (50 - 200 m), some species were reported as typical for. Other studies have examined the influence of the dynamics of the Caribbean on zooplankton community structure (Park, 1970; Owre & Foyo, 1972; Michele & Foyo, 1976; Franco-Herrera, Castro, & Tigreros, 2006; Taylor et al, 2012)
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