Plankton Taxonomic and Size Diversity of Mediterranean Brackish Ponds in Spring: Influence of Abiotic and Biotic Factors

Abstract

In this study, performed in Mediterranean brackish ponds during spring season, we assessed the effects of biotic interactions and abiotic factors on the size and taxonomic structure of the phytoplankton and zooplankton. We used a taxonomic and a size diversity index as a descriptor of the community structure. We predicted that the size diversity of each trophic level would be mainly related to biotic interactions, such as size-based fish predation (in the case of zooplankton) and food resource availability (in the case of phytoplankton), whereas taxonomic diversity would be more affected by abiotic variables (e.g., conductivity, pond morphology). Our results showed a negative relationship between phytoplankton size diversity and food resource availability leading to low size diversities under food scarcity due to dominance of small species. Conductivity also negatively affected the phytoplankton size diversity, although slightly. Regarding zooplankton size diversity, none of predictors tested seemed to influence this index. Similar fish size diversities among ponds may prevent a significant effect of fish predation on size diversity of zooplankton. As expected, taxonomic diversity of phytoplankton and zooplankton was related to abiotic variables (specifically pond morphometry) rather than biotic interactions, which are usually body size dependent, especially in these species-poor brackish environments.

Species Richness and Taxonomic Distinctness of Zooplankton in Ponds and Small Lakes from Albania and North Macedonia: The Role of Bioclimatic Factors

“…Here, we made an attempt towards this direction while using crustacean zooplankton. This group of organisms, ubiquitous in lentic habitats, has been recently subjected to renewed interest as an effective bio-indicator of the environmental status of ponds and small lakes [62][63][64][65]. The heuristic procedure was used here to identify minimum adequate models predicting the diversity the crustacean zooplankton assemblages across the 40 waterbodies under analysis provided non-univocal results.…”

Factors Influencing Abundances and Population Size Structure of the Threatened and Endemic Cyprinodont Aphanius iberus in Mediterranean Brackish Ponds

“…Fish community in the studied ponds is mainly composed by Aphanius iberus and the invasive fish species Gambusia holbrooki [46]. Whereas the former is, overall, more abundant in ponds of higher salinity, the latter is more abundant in oligohaline ponds [46]. The rest of the community is composed by the Atherina boyeri (Risso, 1810), Pomatoschistus sp.…”

“…Hydrological connections among ponds and/or to rivers and the sea take place only during such irregular flooding events [45]. The studied ponds are characterized by their shallowness and cover a range of morphometry (e.g., pond area and depth) and conductivity [46]. Concentrations of inorganic nutrients (nitrates and phosphates) in late-spring are low due to the scarceness of water inputs, but concentrations of total nutrients, especially total nitrogen, are high due to a concentration effect produced by a high evaporation rate [44,45,47].…”

“…In these confined coastal environments, nitrogen, rather than phosphorous, usually limits the primary production [41,48,49]. For more details about the environmental characteristics and planktonic composition of the studied ponds, see [46]. Eight of the studied ponds were located in the "Aiguamolls de l'Empordà" Natural Park (A), and two were located south in the "El Montgrí, Illes Medes i el Baix Ter" Natural Park (B).…”

“…The rest of the community is composed by the Atherina boyeri (Risso, 1810), Pomatoschistus sp. (Gill, 1863), Mugil cephalus (Linnaeus, 1758), the marine fish Solea solea (Queusel, 1806), Anguila anguila (Linnaeus, 1758) and the invasive Lepomis gibbosus (Linnaeus, 1758), although the last three species are very scarce (see [46] for more details on the relative abundance of the fish species).…”