IOV-UDO-ZOOPLANCTON-PLAYA COLORADA

Study Extent

The study area is situated in the marine-coastal region between Playa Arapito and the town of Santa Fe (10°24’N, 64°40’W), which is located in Sucre State, Venezuela, along with the SE Caribbean Sea. The area is an approximately 12 km long and presents sandy beaches, a highly rugged coastline, and a very short continental shelf, which extends offshore from 40 m to 80 m in depth. Similar to northeastern Venezuela, this area is affected by the phenomenon of seasonal coastal upwelling (Okuda, 1975; Alvera-Azcárate et al., 2009; Scranton et al., 2 014), w hich i s c losely r elated t o t he regime of the trade winds, and three climatic periods with different upwelling magnitudes are observed during the year. The first, is a period between December and April, and it presents strong wind intensity (upwelling season) accompanied by low temperature and dissolved oxygen concentrations and high nutrient concentrations; the second, is between May and July (transition period), and it presents a moderate wind intensity and subtropical water; and the third, is between August and November, and it presents the lowest wind intensity (relaxation period), high temperatures and dissolved oxygen concentrations and low nutrient concentrations (Lorenzoni et al., 2013).

Sampling

Sampling was carried out during the survey of the B/O GUAIQUERI II on December 06 and 07, 2008. The stations were located between the coastal areas of the entrance of the Gulf of Santa Fe and the Arapo Islands, which present strong bathymetric gradients. These stations were established in protected areas as zones of a special protection regime (ABRAE) and are part of the Mochima National Park. Samples were collected at 20 stations, which were divided into coastal stations on the continental shelf (stations 3, 5, 9, 12, 14, 20, 23, 26, 28 and 31) and offshore stations in the open sea (greater than 1 km, stations 34, 36, 37, 38, 39, 40, 41, 44, 46 and 49)

Method steps

1. A Bongo mesh net with a pore size of 500 and 300 μm and a mouth diameter of 56 cm was used, and it was equipped with a Rigosha flowmeter. At the coastal stations, daily oblique hauls were performed from the bottom towards the surface; and at the open sea stations, daily oblique hauls were performed from 50 m below the surface to the surface for 15 min at a hauling speed of two knots. The samples were fixed in 5% buffered formalin and transferred to the zooplankton laboratory at the Oceanographic Institute of Venezuela. Abundance was determined by extrapolating the analyzed volume to the original sample. The filtered volume was calculated based on the flowmeter data, which served as the basis for estimating the mesozooplankton abundance per cubic meter of filtered water. To establish the microalgal abundance, samples were taken in each station using Niskin bottles at a depth of 1 m, and they were then poured into plastic bottles (250 ml) and fixed with 4% formalin neutralized with hexamethylenetetramine.
2. Water samples were collected through a conductivity-temperature-depth (CTD) rosette (SBE-19) using 5 L Niskin bottles set at a 5 m depth. The samples (500 ml) were kept frozen (-20°C) until processing and analysis at the Laboratory of Nutrient Elements, Department of Oceanography, Oceanographic Institute of Venezuela. The dissolved oxygen was determined according to the Winkler method described by Strickland and Parsons (1972). The CTD (SBE-19) was used for the vertical recording of temperature and salinity. The concentration of phosphates and nitrates was established according to the recommendations of Gordon et al. (1993). The results for these elements were expressed in μmol L-1.
3. For the zooplankton, each 300 μm mesh sample was homogenized and divided into two equal portions using a Folsom’s Plankton Sample Divider. One part was designated for the study of the community structure and the other for the biomass analysis through the gravimetric method (wet biomass, Postel et al., 2000), without separating the gelatinous organisms. The data were expressed in mg m-3. For the taxonomic determination of the concentrated samples (500 ml), 2.5 ml subsamples were taken with a Stempel pipette. Counting and identification were performed using the works of Tregouboff and Rose (1957), Zoppi (1971), Campos-Hernández and Suárez-Morales (1994) and Boltovskoy (1999), as well as the database of Razouls et al. (2005-2017). For some groups, the most important species were highlighted.

In general, in this work zooplaktonic organisms were identified in large groups, only cladocera species were identified up to species.

1. Pseudoevadne tergestina
   rank: species
2. Penilia avirostris
   rank: species
3. Ostracoda
   rank: class

The study area is situated in the marine-coastal region between Playa Arapito and the town of Santa Fe (10°24’N, 64°40’W; Figure 1), which is located in Sucre State, Venezuela, along with the SE Caribbean Sea. The area is an approximately 12 km long and presents sandy beaches, a highly rugged coastline, and a very short continental shelf, which extends offshore from 40 m to 80 m in depth. Similar to northeastern Venezuela, this area is affected by the phenomenon of seasonal coastal upwelling (Okuda, 1975; Alvera-Azcárate et al., 2009; Scranton et al., 2 014),