Tropical sandy beach meiofauna: a case study on the temporal patterns of a high and low water station in Ecuador

Abstract:

The meiofauna on a cross-shore gradient at an intermediate-reflective Ecuadorian sandy beach was studied fortnightly from June 2000 until July 2001 (this period had undergone a strong La Nina event), in order to analyse the patterns in abundance between upper and lower station at the intertidal zone and to assess the temporal variability in view of seasonality (dry versus rainy season). The sea surface temperature ranged between 21.4 and 27.5 C, the pluviosity was restricted between January and March 2001 (151-114 mm), the salinity ranged between 32 and 34 PSU and the median grain size between 215 and 290 pm at the upper station and 191-301 at the lower station, corresponding to fine-medium sand. The meiofauna samples were collected with plastic cores (3.6 cm diameter) to 20 cm depth. Fifteen meiofauna taxa were registered, with Nematoda the dominant taxon on the beach (61% at the upper station and 83% at the lower station). The total meiofauna density ranged from 186±14 ind./10 cm2 to 3907±408 ind./10 cm 2 at the upper station and from 417±5 ind./10 cm 2 to 1940±166 ind./10 cm 2 at the lower station; however no significant differences on the average meiofauna densities were detected between the stations. Multi-dimensional scaling ordination based on higher meiofauna taxa densities showed cross-shore differences, caused by highest densities of copepods at the upper station (275±86 ind./10 cm2) and highest densities of nematodes (738±64 ind./10 cm 2), with a near absence of copepods at the lower station. At the lower station the total meiofauna and nematode densities showed a significant negative correlation …

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