Holoplankton and meroplankton communities in surf zone waters of a temperate SW Atlantic sandy beach: Seasonal patterns

Abstract

Sandy beaches and their associated surf zones are the most common type of open shoreline, with significant ecological and socio‐economic importance. In this study, we explored the seasonal fluctuations of the surf zone holo‐ and meroplankton communities to understand the underlying environmental variables driving the temporal dynamics of each community. We also defined a surf‐zooplankton community on a temperate sandy beach (Monte Hermoso, Argentina) and related the organisms to those reported in a nearby estuary for a better understanding of the connection between adjacent coastal ecosystems. Holoplankton was very abundant (13.52–11070.4 ind m−3) and showed a strong seasonality, mainly related to the specific pattern of the two most abundant species: Acartia tonsa (>autumn) and Paracalanus parvus (>winter). This community was affected by seasonal changes in water temperature and salinity and variations in the velocity of currents, which showed that hydrodynamic forces were more significant on a short‐term time scale than seasonal ones. Meroplankton abundances (1.3–48.05 ind m−3) were significantly lower than those recorded for the holoplankton and were mainly dominated by Medusae and larvae of Bivalvia and Decapoda. This fraction also showed a clear seasonal pattern (>abundances in summer), primarily related to the seasonal changes in temperature. The abundances of the main surf‐zooplanktonic taxa were high and constant, emphasizing the importance of these waters as habitats for well‐established communities rather than being used as a transient area. Consequently, we proposed a “specific” surf‐zooplankton community for a temperate sandy beach, considering resident and non‐resident taxa. Finally, the comparison of the surf and estuarine communities indicated a faunal relationship between seascapes, highlighting the ecological role of coastal waters in planktonic life.

A life in the surf zone: Age and feeding habits of the pompano (Trachinotus ovatus, Linnaeus, 1758) on the beaches of the Gulf of Cádiz (south‐west Iberian Peninsula)

“…It is also recognized that the abundance of zooplankton has a strong seasonal component in these areas, generally during warm temperature periods (Cunha, 1993;Devreker et al, 2005;Guerreiro et al, 2021). Mysids have peaks of abundance between late spring and autumn (Beyst et al, 2001), and copepods have peaks between late summer and early autumn (Menéndez et al, 2023), which is reflected in the diet of the species, with both groups having a wide presence in these seasons. Similarly, in winter, copepods represented 50% IRI, indicating a high abundance of this group during this season.…”