Abstract:
Introduction: The North Pacific of Costa Rica is characterized by presenting a variation of the subsurface tem-
perature of the sea (SSST) modulated by surface winds with east component, with seasonal and intra-seasonal
variations. The SSST is fundamental for the interactions of the ocean-atmosphere interface and influence marine
biological processes. Zooplankton studies in the North Pacific are scarce and have been focused on the composi-
tion, abundance and biomass of macro and mesozooplankton in Culebra Bay. No works on zooplankton has been
carried out northward of Papagayo Gulf.
Objective: To analyze the variation of the zooplankton in Bahía Salinas at different scales in response to
oceanographic-atmospheric conditions.
Methods: during 2011, 2012 and 2013, mesozooplankton was collected in seven stations following a coastal-
ocean gradient to determine abundance, biomass, and community composition. CTD casts were also carried
out in each station. Hourly data of the Sea Subsurface Temperature (SSST) were obtained from June 2003 to
December 2017.
Results: The annual surface temperature in Bahía Salinas was lower in December-April with a secondary mini-
mum in July and higher in May-June and August-November. The cold, neutral and warm events determined
by anomalies in the SSST, presented a distribution of the temperature in the water column with horizontal
stratification, vertical mixture and homogeneous, respectively. The spatial distribution of zooplankton did not
show significant differences and the variation of the total average abundance and biomass showed a similar
behavior during the study period, with less variation in the first year compared to the second one, being the
copepods the predominant category for all the dates. On a seasonal scale, a general pattern of variation between
dry and rainy seasons was not observed, and copepods and others zooplankton groups were the categories that
presented differences. On an intra-seasonal scale, abundance and biomass showed an inverse relationship with
SST. Copepods and gelatinous zooplankton (GZ) were differentiated in all events.
Conclusions: The zooplankton of Bahía Salinas respond differentially at different scales to the climatic condi-
tions that affect the SSST of the region. The classification of the sampling dates into events allows character-
izing different profiles in the water column it also allows to define the variation patterns for mesozooplankton
that reflects short-term adaptation as a function of variation in environmental conditions. These findings help
to understand how oceanographic processes determine plankton community composition and biota in general.
This is relevant in times of climate change and the manifestation of its impact through processes such as ocean
acidification and loss of marine biodiversity.
