Tidal effects on short-term mesozooplankton distribution in small channels of a temperate-turbid estuary, Southwestern Atlantic

Abstract

The short-term variability of mesozooplankton distribution and physicochemical variables was examined in two different channels of the Bahía Blanca Estuary, Argentina, during two tidal cycles. All the physicochemical measurements and mesozooplankton sampling were performed at a fixed site during approximately 22-23 h at 3-h intervals. Pumps were used to obtain surface and bottom mesozooplankton samples and the water speed of each stratum was measured with an Acoustic Doppler Current Profiler (ADCP). In all, 23 mesozooplanktonic taxa belonging to four phyla (Arthropoda, Annelida, Echinodermata and Chordata) were identified. The most abundant taxa during the two tidal cycles were Balanus glandula larvae, Eurytemora americana and Acartia tonsa. A discernible variability in the water conditions and vertical mesozooplankton distribution (VMD) different from that known for the estuary's main channel, was found in the other two selected channels. VMD varied during the tidal cycle in both channels in accordance with the channel's geomorphology and water dynamic characteristics of each of them. The variation of the abundance of the different taxa during ebb and flood currents might indicate the existence of a tidal vertical migration of the mesozooplankton as a response to particular dynamic water conditions. A variação de curto prazo da distribuição do mesozooplâncton e das variáveis físico-químicas foi examinada em dois diferentes canais do Estuário de Bahia Blanca, Argentina, durante dois ciclos de maré. As medidas físico-químicas e a amostragem do zooplâncton foram realizadas em dois locais fixos durante aproximadamente 22-23 horas, com intervalos de 3 horas. Bombas foram utilizadas para obter amostras de zooplâncton na superfície e no fundo e a velocidade da água em cada estrato foi medida com o Perfilador Acústico de Corrente (ADCP). Ao todo, foram identificados 23 taxa mesozooplanctônicos pertencentes a 4 filos (Arthropoda, Annelida, Echinodermata e Chordata). Os grupos mais abundantes durante os dois ciclos de maré foram larvas de Balanus glandula, além de Eurytemora americana e Acartia tonsa. Nos dois canais selecionados foi identificada uma variação nas condições da água e na distribuição vertical do mesozooplâncton (DVZ) diferente daquela conhecida para o canal principal do estuário. DVZ variou durante o ciclo de maré em ambos os canais de acordo com a geomorfologia e características da dinâmica das águas existente em cada um deles. A variação na abundância dos diferentes taxa durante as marés vazante e enchente poderia estar indicando a existência de migração vertical do mesozooplâncton em resposta a uma determinada condição dinâmica da água. AbstrAct

Distribution and Abundance of Fish Larvae in South of Alas Strait, West Nusa Tenggara

“…Its might related to the migration of fish looking for appropriate environmental conditions and foods availability. Moreover, this condition might the presence of fish larvae was affected by water currents and tides, which distributes fish larvae to various habitats (Chazarreta et al, 2015).…”

Efecto de los efluentes cloacales sobre el ensamble macrobentónico submareal en un estuario urbano de la Argentina

“…Since the estuary is home to the most important deep-water port system of the country, it is also affected by the continuous need for maintenance and dredging operations to accommodate maritime traffic. The physical and chemical changes in sediments produced by sewage effluents have been addressed in several studies (Tombesi et al 2000;Marcovecchio et al 2008;Serra et al 2017) and their effects on the biota have been evaluated through bioindicators such as bacteria (Baldini et al 1999), planktonic communities (Barría de Cao et al 2003Biancalana et al 2012;Dutto et al 2012;Chazarreta et al 2015) and commercial fishes (La Colla et al 2017). Several studies have also been conducted on the concentration of metals in crabs and mollusks inhabiting the intertidal zone of Bahía Blanca estuary (Ferrer 2000;Ferrer et al 2003;Simonetti et al 2012;La Colla et al 2018).…”