Changes in zooplankton diversity and distribution pattern under varying precipitation regimes in a southern temperate estuary

Abstract

a b s t r a c tThe influence of climate variability on the diversity and distribution patterns of zooplankton communities was investigated in the Mondego estuary (Portugal) during four consecutive years characterized by highly variable precipitation and, consequently, river flow regime. Monthly samples were collected along the estuarine gradient at five sampling stations. Seasonal, inter-annual and spatial distributions were evaluated by multivariate analyses and three diversity indices were applied (Species number, Shannon Diversity and Average Taxonomic Distinctness). A two-year drought period presented significant differences in salinity values, especially in 2005 (extreme drought event). During the study period, copepoda was the main dominant group and Acartia tonsa the most abundant species, with the exception of autumn 2006, where high abundances of the cladoceran Penilia avirostris were noticed. Multivariate analysis indicated that zooplankton communities changed from a pre-to a post-drought period indicating the influence of hydrological parameters in communities' structure. The dry period was associated with an increase in zooplankton density, a reduction in seasonality and higher abundance and prevalence of marine species throughout the year. Seasonally, winter/spring communities were distinct from those in summer/autumn. Spatially, salinity-associated differences between upstream and downstream communities were reduced during the drought years, but during the post-drought year, these differences were detected again.

Seasonal dynamics of plankton communities coupled with environmental factors in a semi arid area: Sidi Sad reservoir (Center of Tunisia)

“…A positive correlation was observed between zooplankton abundance and temperature (r = 0.53, p = 0.027, n =16). This is in accordance with the study of Primo et al (2009) concluding that water temperature was the main factor influencing the spatial and temporal patterns of zooplankton distributions. Furthermore, not much variation in pH values was observed.…”

Seasonal changes in the abundance and biomass of zooplankton from shallow mudflat river-estuarine system in Persian Gulf

“…The copepod, mostly calanoid, was the dominant assemblage in HR estuary. Similar zooplankton groups were common in other estuaries (Tiwari and Nair, 1993;Wooldridge and Callahan, 2000;Primo et al, 2009;Hwang et al, 2010;Xuelu et al, 2011). In fact, distribution of zooplankton populations is mostly governed by various behavioral and physiological adaptations to ever changing hydrographical conditions (Mohan et al, 1999).…”

Zooplankton of the St. Lucia Estuary during the current drought cycle: a comparison between open- and closed-mouth conditions

“…Missing components included marine and freshwater taxa, which were absent because of prolonged reduced freshwater input (Allanson & Read 1995) and the closed-mouth state which prevented tidal exchange. Primo et al (2009) Table 3 (continued) diversity and a high density of Acartia spp. However, in contrast to the St. Lucia system, marine taxa dominated the Mondego Estuary, probably due to its open mouth (Primo et al 2009).…”

“…Primo et al (2009) Table 3 (continued) diversity and a high density of Acartia spp. However, in contrast to the St. Lucia system, marine taxa dominated the Mondego Estuary, probably due to its open mouth (Primo et al 2009). The opening of the St. Lucia Estuary mouth in March 2007 led to a great increase in species richness.…”