Hydrobiologia

Lefrancois, Estelle; Labeille, Marion; Marquès, Joévin; Robert, Marie; Valentini, Alice

doi: 10.1007/s10750-024-05476-8pmid: N/A

Freshwater biodiversity is rapidly declining worldwide, especially in tropical island environments which appear to be particularly vulnerable to alien species. Monitoring biodiversity using effective methods is crucial for conservation efforts. This study aims to examine the capacity of the eDNA-based method to provide accurate measures of fish and crustacean biodiversity, and how it can be implemented in the French West Indies. To this end, we conducted eDNA and electric fishing capture-based surveys in parallel, both upstream and downstream, in nine Guadeloupean rivers and during two different seasons. While both methods were congruent in terms of species richness and composition, the eDNA-based method generally exhibited greater efficacy and reliability in assessing biodiversity. The exception to this trend was observed during the second campaign for the crustacean community. The quantitative data (the numbers of individuals and percentages of sequences) also proved to be uncorrelated for crustaceans during the second campaign, indicating that further knowledge of crustacean biology is needed. Nevertheless, the eDNA-based method was able to detect the presence of alien, rare and cryptic species, showing that it can be used in tropical island conditions for biodiversity assessment or conservation purposes.

Lemos, Liliam de Lima; Bornatowski, Hugo; Freitas, Renato Hajenius Aché de

doi: 10.1007/s10750-024-05494-6pmid: N/A

We aimed to characterize the trophic ecology and test the hypothesis of niche overlap between four sympatric batoid species of the subtropical South Atlantic. Data were collected between 2017 and 2022 from two artisanal fishery communities in southern Brazil. Batoid’s stomach contents were identified, separated into categories, and weighed. We calculated the Levins, Pianka’s, and Prey-specific index of relative dietary importance (PSIRI) and performed a similarity test using PERMANOVA and the similarity percentage (SIMPER) for niche analysis. We analyzed 229 stomachs of four batoid species, 187 containing foods. All species showed a narrow food niche. The most important diet items for each species were Leptochaela serratorbita and Onuphidae for Dasyatis hypostigma; Nematoda for Pseudobatos horkelii; L. serratorbita, Sicyonia dorsalis and Portunidae for Rioraja agassizii and Achelous spinicarpus and fish for Sympterygia bonapartii. The analyses showed dissimilarity among the species’ diets without significant niche overlap. Our results detected the absence of significant niche overlap among batoid species, suggesting other types of niche partitioning and spatiotemporal habitat variation. This information could be considered for local management plans.

Lemos, Liliam de Lima; Bornatowski, Hugo; Freitas, Renato Hajenius Aché de

doi: 10.1007/s10750-024-05535-0pmid: N/A

García-Cobo, Marta; González-Casarrubios, Alberto; García-Gómez, Guillermo; Pardos, Fernando; Sánchez, Nuria

doi: 10.1007/s10750-024-05495-5pmid: N/A

Nematodes typically comprise the most abundant phylum in meiofaunal communities. We aim to characterize the specific ecological conditions that influence Nematoda communities in Posidonia oceanica grasslands focusing on three habitats: leaves, matte, and unvegetated adjacent sediment. We hypothesized that the constant flux of nutrients under the canopy would result in a higher concentration of metazoans compared to the unvegetated sediment outside; however, the hypothesis was not confirmed by the obtained results. The habitat heterogeneity played an important role in shaping the community, yielding a greater richness in the matte. The resource specificity of the leaves (microepiphytes) was also expected to shape the community by favoring nematodes capable of exploiting this resource (epistratum feeders with scraping-like structures), such as the family Chromadoridae that dominated this habitat. In addition, the high light exposure of the leaves explains the higher concentration of ocellated nematodes in this habitat. Organic carbon and nitrogen contents had an impact on the Nematoda community composition, meanwhile average grain size only affected the abundance of nematodes with elongated/filiform tails.

Pezzato, Maura Maria; da Cunha-Santino, Marcela Bianchessi; Camargo, Antonio Fernando Monteiro; Bianchini, Irineu

doi: 10.1007/s10750-024-05496-4pmid: N/A

Understanding the factors that control the growth of macrophytes is of paramount importance in predicting their distribution and management. This study describes the effect of short-term variation of pH, light intensity (10–390 µmol m−2 s−1), and temperature (15–30 °C) over the gross photosynthetic rate, respiration rate and net photosynthetic rate (NP) of Egeria najas in nutrient limited condition, and high nutrient availability. The light and dark bottles method was utilized to measure photosynthesis. The pH increase from 4.0 to 8.5 promoted a continuous decrease in NP. Temperature had an important effect on the NP value, with variations in Q10 from 1.42 to 2.23. Although maximum NP rates occurred under low light intensity (158–204 µmol m−2 s−1), in short-term, the availability of light can represent the main factor controlling photosynthesis in rooted E. najas; nevertheless, dissolved nutrients can highly induce the growth of free-float specimens. Our results facilitate the understanding of E. najas potential to colonize since it easily adapts to changes in environmental conditions.

Gregory, C.; Cave, Rachel R.; Raine, R.; McDermott, G.

doi: 10.1007/s10750-024-05497-3pmid: N/A

A near-unique pair of adjacent bays in the karst region of western Ireland provided the opportunity to compare phytoplankton diversity and abundance in an area of submarine groundwater discharge (SGD) side by side with a ‘control’ region of similar size and with the same marine influences. Freshwater input to Kinvara Bay comes from the surrounding karst hinterland via a subterranean groundwater network, emerging at several sites within the inner bay as submarine groundwater discharge (SGD). Aughinish Bay in contrast has no connection to a SGD network and negligible overground fresh water input. Sampling was carried out in both bays during spring and neap tides over Winter, Spring/Summer and Summer/Autumn of 2016 and 2017. Comparison of the phytoplankton communities in the two bays showed higher diversity in Aughinish, while a bloom of Prorocentrum micans (Ehrenber, 1834), a brackish-water-tolerant marine dinoflagellate, was observed only in Kinvara. This work demonstrates how SGD can control phytoplankton community structure even in well-flushed macro-tidal bays and thus controls the biogeography at local scales.

Sabel, Maike; Yohannes, Elizabeth; Straile, Dietmar; Rothhaupt, Karl-Otto

doi: 10.1007/s10750-024-05500-xpmid: N/A

Changing nutrient concentrations and introduction of non-native species affect the energy and nutrient fluxes in aquatic ecosystems. As a response, invertebrate communities could be altered, and ‘novel’ trophic communities could develop. Lake Constance (Europe) experienced pronounced nutrient variation caused by cultural eutrophication (prior 1980s) and oligotrophication (post-1980) and experienced many neobiota invasions. We used archived samples to investigate the impact of oligotrophication and invasive species on carbon and nitrogen isotope signatures of littoral macroinvertebrates during spring and autumn periods from 2000 to 2015 and of littoral fish species in 2018. Isotopic signatures of invertebrate and fish species were in the same range and showed similar seasonal differences and clear patterns in respect to littoral vs pelagic food sources and trophic level. Oligotrophication did not strongly alter isotopic values and only δ15N values of invertebrates declined weakly with oligotrophication. In contrast, interannual variability of stable isotope signatures was related to abundances of the invasive Dreissena polymorpha suggesting interannual differences in the importance of benthic-pelagic coupling due to Dreissena pseudofaeces for the nutrition of littoral invertebrates. This study illustrates how stored samples can be used to detect the importance of oligotrophication and benthic-pelagic coupling on the stable isotope signatures of a benthic community.

Garcia-Cardenas, Eduardo Everardo; Angeles-Gonzalez, Luis Enrique; Alcaraz, Guillermina

doi: 10.1007/s10750-024-05501-wpmid: N/A

The fundamental ecological niche is determined by individuals’ ability to cope with abiotic conditions; however, biotic interactions (e.g., competition) can also influence species’ distribution ranges, reducing the fundamental niche to the realized niche. Several species of the genera Clibanarius and Calcinus overlap in their distributions. The agonistically dominant Calcinus species inhabits mostly lower intertidal levels, while Clibanarius is more abundant in the abiotically demanding upper strata. Additionally, evidence of microhabitat competitive exclusion shows that the superior competitor, Ca. californiensis, causes the vertical displacement of Cl. albidigitus. However, it is unknown whether competitive exclusion between species of these genera has influenced their distributions at the macroecological scale. We used ecological niche models to compare the distribution and the habitat suitability of species of these genera. We used databases of species occurrences and bioclimatic and geophysical variables to model and map the species’ niches. Species of the two hermit crab genera showed strong overlap in their habitat suitability. Calcinus and Clibanarius species occur in broad sympatry at the regional scale without regions of partial overlap that would indicate competitive exclusion. Therefore, competitive exclusion among species of these genera seems to act only on a microhabitat scale in the most dynamic shoreline areas.

Qiao, Jialing; Zhang, Dong; Wu, Yongsheng; Zhang, Chen; Chu, Ling; Yan, Yunzhi

doi: 10.1007/s10750-024-05502-9pmid: N/A

Anthropogenic land use has caused a major crisis to the biodiversity of stream fishes in recent decades, especially with regard to biotic homogenisation. Understanding the response of stream fishes to anthropogenic land use will help to promptly implement effective conservation measures. In this study, we investigated the effects of agriculture on fish diversity in streams in the Wannan Mountains, China. We predicted that agriculture would influence fish diversity by affecting local habitat conditions. The results showed that habitat conditions (e.g. water temperature, water width, water depth) differed significantly between disturbed and reference sites. The disturbed sites had high species richness due to the addition of translocated species outpacing the loss of endemic species. Moreover, fish assemblages showed taxonomic differentiation accompanied by functional homogenisation, which mainly resulted from the addition of translocated species with redundant functional traits. However, the emergence of homogenisation shows a time delay. The biotic differentiation of fish assemblages in agroecosystems is temporary in the Wannan Mountains, and homogenisation may eventually develop as stress intensifies. Thus, it is urgent and necessary to take effective conservation measures to delay or prevent fish assemblages from worsening in agroecosystems before homogenisation develops.

Makiguchi, Yuya; Iimura, Yukiyo; Nakao, Katsuya; Nii, Hisaya; Ueda, Hiroshi; Nagata, Mitsuhiro

doi: 10.1007/s10750-024-05503-8pmid: N/A

The Japanese crayfish, Cambaroides japonicus (De Haan, 1841), listed as endangered due to dramatic population declines, necessitates an understanding of its movement patterns and home ranges for effective conservation. This study tested specific hypotheses using portable and fixed passive integrated transponder (PIT) tagging systems to characterize the species’ long-term movement patterns. We hypothesized that movement would be size-dependent and exhibit seasonality. Our findings confirmed these hypotheses, showing most tracked individuals either migrated upstream, reflecting a size-dependent movement, remained stationary near the release point, or ventured downstream. Analysis revealed the total movement range to be approximately 69 m, consisting of a maximum upstream movement of 47.4 m and a downstream movement of 21.6 m. Notably, the cumulative and maximum distances traveled were positively correlated with the size of both male and female crayfish throughout the observation period. Seasonal patterns emerged as well, with some individuals, especially males, moving downstream during overwintering. This pioneering study reveals the seasonal movement patterns of Japanese crayfish for the first time, supporting the hypothesis of size-dependent and seasonal movement. These insights are crucial for developing targeted habitat and species conservation strategies.