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Palud is a natural depression in the southwest of the Istrian peninsula (N Adriatic Sea, Croatia), situated by the sea and transformed into a marsh by the inflow of water from the adjacent hills. At the beginning of the 20th century, the marsh was connected to the sea by an artificially dug channel to control mosquitoes (vectors of malaria). This led to the brackish conditions in the marsh. The objective of this pilot-study was to investigate the rotifer community composition in Palud Marsh during the summer of 2021. Zooplankton samples were collected at two-week intervals during July 2021 at the four sampling sites that extend along the Palud salinity gradient. Water physicochemical factors analysis showed a significant trend along the salinity gradient indicating a decrease in plankton productivity in July, likely caused by a decrease in Palud water depth due to runoff from the marsh to the sea. Only a very small number of taxa (6) were found in the plankton. Rotifers were represented by three taxa (Brachionus plicatilis, Encentrum sp., Lecane lunaris). Of all individuals recorded, 97.3% belonged to B. plicatilis, a cosmopolitan eurythermal species and a halobiont (i.e., it prefers saline shallow waters and lagoons). This pilot-study was the first step in assessing the ecological conditions of Palud Marsh. Further studies are necessary to develop effective conservation measures for this protected habitat, which was declared a special ornithological reserve in 2001.

Diptera, with their participation in pollination, significantly contribute to the maintenance of plant diversity, and they also have great potential for assessing habitat health and preserving it. A decline in their abundance and diversity has been recorded worldwide as a consequence of biotic, abiotic, and anthropic alterations. In addition to pollinators, these orders include agricultural and forestry pests, which are a threat to both cultivated and wild plants that are very important to the economy. Many pests have escaped from their native areas, and it is important to monitor their spread to implement sustainable means of control. Our study provides baseline information on Diptera and Vespidae diversity in the Mediterranean mosaic of agroecosystems, giving information on the importance of human influence on insect diversity. We carried out an insect inventory in Istria, Croatia, using a set of traps placed in the proximity of beehives. This study was also important in determining the presence of pests and newly introduced species. A total of 94 species from 24 families were recorded—7 important agricultural pests of Diptera and 17 new records for Croatia. The correlation between species diversity and environmental and anthropogenic factors leads to the conclusion that total insect species richness, pest species richness, and the first findings depend on human activities. The number of honeybee colonies negatively correlated with species richness, while anthropic influence positively affected total and pest species richness.