Natural or anthropogenic variability? A long-term pattern of the zooplankton communities in an ever-changing transitional ecosystem

The Venice Lagoon is an important site belonging to the Italian Long-Term Ecological Research Network (LTER). Alongside with the increasing trend of water temperature and the relevant morphological changes, in recent years, the resident zooplankton populations have also continued to cope with the colonization by alien species, particularly the strong competitor Mnemiopsis leidyi. In this work, we compared the dynamics of the lagoon zooplankton over a period of 20 years. The physical and biological signals are analyzed and compared to evaluate the hypothesis that a slow shift in the environmental balance of the site, such as temperature increase, sea level rise (hereafter called “marinization”), and competition between species, is contributing to trigger a drift in the internal equilibrium of the resident core zooplankton. Though the copepod community does not seem to have changed its state, some important modifications of structure and assembly mechanisms have already been observed. The extension of the marine influence within the lagoon has compressed the spatial gradients of the habitat and created a greater segregation of the niches available to some typically estuarine taxa and broadened and strengthened the interactions between marine species

Meta-analysis of multidecadal biodiversity trends in Europe

Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15-91 years) collected across Europe, using a comprehensive dataset comprising similar to 6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe. The global biodiversity decline might conceal complex local and group-specific trends. Here the authors report a quantitative synthesis of longterm biodiversity trends across Europe, showing how, despite overall increase in biodiversity metric and stability in abundance, trends differ between regions, ecosystem types, and taxa.peerReviewe

The Copepod Acartia tonsa Dana in a Microtidal Mediterranean Lagoon: History of a Successful Invasion

The Lagoon of Venice has been recognized as a hot spot for the introduction of nonindigenous species. Several anthropogenic factors as well as environmental stressors concurred to make this ecosystem ideal for invasion. Given the zooplankton ecological relevance related to the role in the marine trophic network, changes in the community have implications for environmental management and ecosystem services. This work aims to depict the relevant steps of the history of invasion of the copepod Acartia tonsa in the Venice lagoon, providing a recent picture of its distribution, mainly compared to congeneric residents. In this work, four datasets of mesozooplankton were examined. The four datasets covered a period from 1975 to 2017 and were used to investigate temporal trends as well as the changes in coexistence patterns among the Acartia species before and after A. tonsa settlement. Spatial distribution of A. tonsa was found to be significantly associated with temperature, phytoplankton, particulate organic carbon (POC), chlorophyll a, and counter gradient of salinity, confirming that A. tonsa is an opportunistic tolerant species. As for previously dominant species, Paracartia latisetosa almost disappeared, and Acartia margalefi was not completely excluded. In 2014–2017, A. tonsa was found to be the dominant Acartia species in the lagoon

The non\u2011indigenous Oithona davisae in a Mediterranean transitional environment: coexistence patterns with competing species

The Venice lagoon (VL) has been recognized as a hot spot of introduction of non-indigenous species (NIS), due to several anthropogenic factors and environmental stressors that combined may facilitate NIS invasions. In the last decades an increasing number of zooplankton NIS have been observed in the VL. This work aims to provide a picture of the annual cycle and distribution of the recently recorded non-indigenous copepod Oithona davisae, considering the coexistence patterns with the congeneric resident Oithona nana. Therefore, zooplankton samplings were carried out monthly from August 2016 to July 2017 at five Long-Term Ecological Research LTER stations in the VL. Oithona davisae showed a persistent occurrence throughout the year with the highest abundances in the warm season and in the inner areas, while the congeneric O. nana, showing a different distribution pattern, resulted more abundant near the inlets of the Lagoon, where O. davisae reached the minimum density. Oithona davisae seems to find local conditions that promote its settlement and distribution, especially in the inner and more trophic lagoon sites. In other European coastal embayments or transitional waters, O. davisae occupied the niche left by the indigenous O. nana or can replace this congeneric species through competitive exclusion mechanisms. Our data indicate that, for now, such species replacement has not occurred in the VL. One of the causes is the extreme variety of habitats and niches offered by this environment allowing a balanced coexistence with O. nana and in general with the resident copepod community

The Copepod Acartia tonsa Dana in a Microtidal Mediterranean Lagoon: History of a Successful Invasion

The Lagoon of Venice has been recognized as a hot spot for the introduction of nonindigenous species. Several anthropogenic factors as well as environmental stressors concurred to make this ecosystem ideal for invasion. Given the zooplankton ecological relevance related to the role in the marine trophic network, changes in the community have implications for environmental management and ecosystem services. This work aims to depict the relevant steps of the history of invasion of the copepod Acartia tonsa in the Venice lagoon, providing a recent picture of its distribution, mainly compared to congeneric residents. In this work, four datasets of mesozooplankton were examined. The four datasets covered a period from 1975 to 2017 and were used to investigate temporal trends as well as the changes in coexistence patterns among the Acartia species before and after A. tonsa settlement. Spatial distribution of A. tonsa was found to be significantly associated with temperature, phytoplankton, particulate organic carbon (POC), chlorophyll a, and counter gradient of salinity, confirming that A. tonsa is an opportunistic tolerant species. As for previously dominant species, Paracartia latisetosa almost disappeared, and Acartia margalefi was not completely excluded. In 2014–2017, A. tonsa was found to be the dominant Acartia species in the lagoon

Pseudodiaptomidae G.O. Sars., 1902

The family Pseudodiaptomidae G.O. Sars, 1902 includes three genera: Calanipeda Kritschagin, 1873, Pseudodiaptomus Herrick, 1884, and Archidiaptomus Madhupratap and Haridas, 1978. The genera Calanipeda and Archidiaptomus are both monotypic, consisting of Calanipeda aquaedulcis and Archidiaptomus arroorus respectively, whereas the genus Pseudodiaptomus includes 78 valid species (Walter and Boxshall, 2023). Pseudodiaptomus is divided up into seven species groups, and eight species subgroups can be distinguished based on the key to species groups and subgroups reported (Walter, 1986a; Walter et al., 2006; Srinui et al., 2013).Calanipeda aquaedulcis is a freshwater euryhaline species and usually occurs in rivers, lakes, and estuaries around the Mediterranean Sea, Black Sea, and Caspian Sea regions as well as Spanish, and Portuguese waters (Razouls et al., 2005–2023). Archidiaptomus arroorus is found in brackish coastal waters of India (Madhupratap and Haridas, 1978). Pseudodiaptomus species are spread over a broad latitudinal range worldwide and are typically found in tropical and temperate shallow coastal and estuarine waters (Walter, 1989). They usually occur in a range of salinity, from hypersaline, marine to freshwaters (Walter, 1986a).To date, in both the ICES area and the Black Sea, among Pseudodiaptomidae species, Pseudodiaptomus marinus Sato, 1913 and C. aquaedulcis occur, whereas in the Mediterranean Sea these two species occur in addition to Pseudodiaptomus salinus Giesbrecht, 1896, Pseudodiaptomus trihamatus Wright S., 1937, Pseudodiaptomus australiensis Walter, 1987, and Pseudodiaptomus arabicus Walter, 1998. (Razouls et al., 2005–2023). A key modified from Boxshall and Halsey (2004) for the identification of the three genera included in the family Pseudodiaptomidae, a key for the identification of the five species included in the genus Pseudodiaptomus, and the morphological features of C. aquaedulcis are presented.The aim of this leaflet is to help with the morphological identification of the species of Pseudodiaptomidae present in the ICES area as well as in the adjacent Ponto-Mediterranean region and to provide their geographic distribution. This is a new leaflet and shows an unedited stereomicroscope image of a P. marinus egg-carrying female (Figure 1).</p

Suitability of a dual COI marker for marine zooplankton DNA metabarcoding

As DNA metabarcoding has become an emerging tool for surveying biodiversity, including its application in legally binding assessments, reliable and efficient barcodes are requested, especially for the highly diverse group of zooplankton. This study focuses on comparing the efficiency of two mitochondrial COI barcodes based on the internal primers mlCOIintF and mlCOIintR utilizing mesozooplankton samples collected in a Mediterranean lagoon. Our results indicate that after a slight adjustment, the mlCOIintR primer performs in combination with jdgLCO1490 (herein) very comparably to the much more widely used primer system mlCOIintF/ jgHCO2198+dgHCO2198, in terms of level of taxonomic resolution, species detection and their relative abundance in terms of numbers of reads. As for some groups, like Ctenophora, this barcode is not suitable; a combination of them may be the best option to rely on the Folmer region in its entirety without the risk of losing information for a limited primer match

DNA METABARCODING FOR ZOOPLANKTON BIODIVERSITY ASSESSMENT THE CLASSICAL VS. THE MOLECULAR APPROACH

Zooplankton biodiversity assessment is a crucial element in monitoring marine ecosystem processes and community responses to environmental alterations. As morphological assessments of zooplankton assemblages are labour intensive, the characterization of the spatio-temporal variability would often require an unsustainable effort. The rising necessity for taxonomic information across trophic levels to support ecological research and ecosystem-based management efforts asks for fast and cost-effective methods for biodiversity assessment. Therefore, thanks to its advantage of increased sample processing speed and the broad taxonomic coverage, DNA metabarcoding is becoming an important tool for surveying marine biodiversity. It is a molecular approach for taxonomic identification, based on the sequencing of a DNA fragment, the barcode, that is unique to each species and can therefore be used for species discrimination. The present study aims to evaluate the suitability of DNA metabarcoding for zooplankton biodiversity assessment comparing it to the classical morphological method. Therefore, seasonal zooplankton sampling at six stations was carried out in 2016/17 in the Venice Lagoon and the nearby coastal area and each sample was analysed with morphological analysis and with molecular analysis. Compared to the morphological identification, DNA metabarcoding resulted in more taxa being resolved at species level (84% vs. 46% of assignments) and higher taxonomic richness (224 vs. 88 taxa), especially regarding mero-, ichthyoplankton and cryptic species. However, the ecological analysis resulted in very similar patterns comparing the two methods, certainly the molecular identification of the zooplankton community distinguished better between seasons. Especially in large-scale monitoring programs and biodiversity assessments of ecosystems with high spatial and temporal variability, where high sampling effort is required, DNA metabarcoding seems to be a promising tool