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Short-term responses to sewage discharge and storms of subtidal sand-bottom macrozoobenthic assemblages off Mar del Plata City, Argentina (SW Atlantic)
Elías, R.; Palacios, J.R.; Rivero, M.S.; Vallarino, E.A. (2005). Short-term responses to sewage discharge and storms of subtidal sand-bottom macrozoobenthic assemblages off Mar del Plata City, Argentina (SW Atlantic). J. Sea Res. 53(4): 231-242.
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101, more
Peer reviewed article  

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    Behavioural responses; Macrobenthos; Sewage disposal; Short-term changes; Storms; Zoobenthos; PSW, Argentina, Buenos Aires, Mar del Plata; Marine

Authors  Top 
  • Elías, R.
  • Palacios, J.R.
  • Rivero, M.S.
  • Vallarino, E.A.

    This work describes short-term responses of sandy-bottom infaunal macrobenthic communities to environmental disturbances, such as episodic storms and the intertidal sewage discharge of the Mar del Plata City (38° S, 57° W, Argentina). Sewage discharge increases by up to 60% every summer due to tourism pressure. Episodic storms affect the area during autumn-winter and arguably have a cleaning effect on the water and sediment quality. Quantitative data on benthic communities (based on Van Veen grab samples), water and sediment variables were obtained in November 1999 and March 2000. During March the sampling was carried out before and after a storm. Parametric and non- parametric tests showed highly significant differences in both environmental (pH, dissolved oxygen, salinity, temperature, grain size and total organic carbon of sediments) and biological data (species distribution and abundances, density, species number, diversity and evenness), reflecting changes that might be related to increasing sewage discharge between November and March, and to storm effects of March. High values of pH and dissolved oxygen, including a slight stratification in the water column, as well as high values of mean grain size and total organic carbon were observed in March with the increasing sewage volume. Nevertheless, diversity and evenness showed low values, but higher density. The ratio crustacean/polychaetes + molluscs also showed low values compared to November data. Maldanid polychaetes (indicator of low content of organic matter in sediments) dominated in November, but they were replaced by the polychaete Prionospio spp. (indicator of organic enrichment in subtidal areas) and the tanaidacean Kalliapseudes schubarti in March. Before the storm event, values of both environmental and biological data returned to relatively normal conditions, but without reaching the November values, reflecting the disturbance produced by a moderate northern storm. In spite of an inappropriate replication in time, the present results strongly suggest that these changes were related to both sewage disturbance and storm effects. These data are in agreement with and explain the pattern observed in shallow-shelf benthic communities of the SW Atlantic. Implications for environmental management and decision making are discussed, because a pulse disturbance (storms) becomes a press disturbance, keeping the environment healthy in spite of strong pressure and pulse sewage-disturbances.

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