Seasonal Variability in the Distribution of Phytoplankton in Paracas Bay/Peru, as a Response to Environmental Conditions

Abstract

During 2013-2015, a series of bio-oceanographic surveys was carried out in Paracas bay (13°50′ S). This coastal habitat represents a transition between open ocean and continent. Changes in distribution and structure of phytoplankton community and presence of noxious algal blooms were evaluated. The vertical stability of water column was analyzed on transects of temperature, salinity and potential density. Stratification of the water column as well as other variables presented a seasonal behavior. The maximum values were recorded in summer and were directly related to the seasonal heat flux in surface layers of the bay, while in winter this stratification index was minimum. N/P ratios showed a seasonal variation with highest values in winter and lowest ones in summer. Silicate concentrations were minimum mainly during in spring due to high biological fixation. The dominance of diatoms was evident in winter and spring, with maximum abundances of r strategists. The diversity and equitability indexes were low (< 3 bitscel-1 and 0.31, respectively). During summer, there was a greater contribution of oceanic species, with high concentrations of the dinoflagellate Prorocentrum cordatum; and a higher frequency of algal blooms (Akashiwo sanguinea, Heterosigma akashiwo, Eutreptiella gymnastica and Gonyaulax polygramma) in the coastal zone. Silicates and pH presented a significant correlation with diatom abundances in spring, whilst dinoflagellates were associated to warm and salinity conditions in summer. Weak correlations were found for potentially toxic dinoflagellates with temperature and for Pseudo-nitzschia group with silicates and phosphates.

Out of the depths: new records of the sea anemone Oulactis coliumensis (Riemann-Zürneck & Gallardo, 1990) in shallow waters from northern Chile and Peru

“…Both Callao and Paracas (Peru), as well as Tocopilla and Concepcion (Chile), harbour large tonnage ports that receive vessels from around the world. All four sites are located in sheltered bays, with an average seawater temperature that generally ranges between 15.4–16.9°C in Callao (Graco et al ., 2019), 18.1–25.3°C in Paracas (Sánchez et al ., 2018), 13.5–17.7°C in Tocopilla (CENDHOC, 2021) and 10.4–16.0°C near Concepción (CENDHOC, 2021). As it is seasonally affected by intense upwelling episodes, dissolved oxygen especially fluctuates throughout this region and can vary from below 0.5 to more than 7 mg l −1 .…”