Water resources are critically important, but also pose risks of exposure to toxic and pathogenic microbes. Increasingly, a concern is toxic cyanobacteria, which have been linked to the death and disease of humans, domesticated animals, and wildlife in freshwater systems worldwide. Management approaches successful at reducing cyanobacterial abundance and toxin production have tended to be short-term solutions applied on small scales (e.g., algaecide application) or solutions that entail difficult multifaceted investments (e.g., modification of landscape and land use to reduce nutrient inputs). However, implementation of these approaches can be undermined by microbial species interactions that (a) provide toxic cyanobacteria with protection against the method of control or (b) permit toxic cyanobacteria to be replaced by other significant microbial threats. Understanding these interactions is necessary to avoid such scenarios and can provide a framework for novel strategies to enhance freshwater resource management via systems science (e.g., pairing existing physical and chemical approaches against cyanobacteria with ecological strategies such as manipulation of natural enemies, targeting of facilitators, and reduction of benthic occupancy and recruitment). Here, we review pertinent examples of the interactions and highlight potential applications of what is known.

Documenting flow regimes and the ecology of source headwater streams has gained considerable attention for scientific and regulatory purposes. These streams do not appear on standard maps, and local physiographic and climatologic conditions can control their origins. We investigated macroinvertebrate assemblages seasonally and in relation to flow duration, catchment and habitat variables within 14 source headwaters (< 1 ha) in the Western Allegheny Plateau over a 19-month period. We classified 6 perennial () and 8 intermittent () streams directly with continuous flow data loggers. Several biological and trait-based metrics could distinguish flow class, but few instream physical measures could. Macroinvertebrate metrics and assemblage dispersion varied seasonally and responded significantly along a gradient of total flow duration. Separate indicator species analyses generated 22 genera and 15 families with significant affinities to streams. Richness of indicator taxa was also strongly correlated with flow duration gradients, and we estimated a total flow duration changepoint at 77% (3 indicator families) followed by a sharp increase in richness. Two rapid field-based flow duration methods (NC Stream Identification index and OH Headwater Habitat Evaluation index) could distinguish upstream ephemeral reaches from and reaches, but misclassified as more frequently. Our findings highlight that diverse coldwater macroinvertebrate assemblages inhabited extremely small, low-discharge springs in the region, and responded with flow duration. These source headwater habitats are susceptible to human disturbance and should be monitored as is routinely done in larger lotic systems.

Cyanobacteria have multifaceted ecological roles on coral reefs. , a chemically rich filamentous cyanobacterium, has been characterized as a pathogenic organism with an unusual ability to overgrow gorgonian corals, but little has been done to study its general growth habits or its unique association with the snapping shrimp . Quantitative benthic surveys, and field and photographic observations were utilized to develop a better understanding of the ecology of these species, while growth experiments and nutrient analysis were performed to examine how this cyanobacterium may be benefiting from its shrimp symbiont. Colonies of and displayed considerable habitat specificity in terms of occupied substrate. Although found to vary in abundance and density across survey sites and transects, was consistently found to be thriving with within interstitial spaces on the reef. Removal of from cyanobacterial colonies in a laboratory experiment altered pigmentation, whereas cyanobacteria-shrimp colonies in the field exhibited elevated nutrient levels compared to the surrounding seawater.

Harmful algal blooms (HABs) pose substantial health risks to seafood consumers, drinking water supplies, and recreationalists with apparent increases associated with anthropogenic eutrophication of freshwaters and coastal areas. Attempts to intervene in these blooms can be met with reticence by citizens, non-governmental organizations, and officials, often due to local perceptions and beliefs. Hence, the social sciences have an important role to play in HAB research and mitigation. Much of the social science HAB research to date has focused on how best to communicate associated risks and appropriate behavioral responses to affected local communities. The emphasis has been on the direct human impacts, particularly in the areas of health outcomes and identification of any sociocultural and economic barriers to proposed mitigation. While this focus is warranted and valuable, there is also a need to understand HABs as part of a larger human-environmental coupled system, where blooms trigger a wide range of cultural and behavioral responses that are driven by how blooms impact other social and ecosystem dynamics. The research presented here describes a case study of a bloom in a lake in the Chesapeake Bay watershed where anthropologists worked with HAB researchers. The results of this interdisciplinary collaboration show that approaching the bloom and mitigation within a 'socio-ecological systems' framework provides stakeholders with a range of rationales and approaches for addressing HAB mitigation, enhancing both short-term successes and longer-term opportunities, even if is still present in the lake.

In this study, we tested the hypothesis that the growth efficiency of freshwater bacteria is differentially affected by ultraviolet radiation (UVR, 280-400 nm) as mediated through changes in their production and respiration rates. Five bacterial strains affiliated to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria were isolated from different freshwater habitats and exposed in the laboratory to photosynthetically active radiation (PAR) and PAR + UVR, or kept in the dark for 4 h. Afterward, bacterial carbon production and respiration were assessed by measuring leucine incorporation and oxygen consumption rates, respectively. Ultraviolet radiation decreased significantly the bacterial production of Acidovorax sp., Pseudomonas sp. and Actinobacterium MHWTa3, and the respiration rate of Acidovorax sp. and Acinetobacter lwoffii. Measurements of respiration of a natural bacterial community collected from the same lake where A. lwoffii was isolated resulted in significantly higher rates after exposure to PAR + UVR than in the dark. In the presence of UVR, bacterial growth efficiency significantly decreased in Acidovorax sp., Pseudomonas sp., and Actinobacterium MHWTa3, but it increased in A. lwoffii or it remained unchanged in Sphingomonas sp. Our results indicate that although the outcome was strain-specific, UVR has the potential to alter the efficiency by which dissolved organic matter is transformed into bacterial biomass and thus to affect the biogeochemical carbon cycle.

Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967-2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the 'Northern Peel region', a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (, Linnaeus 1758) and preferred by nine-spined stickleback (, [Linnaeus, 1758]). After 1979, the separation between both sticklebacks became weaker, corresponding to a decreased influence of local groundwater on stream water quality. The way both species changed their distribution in the field provides a strong indication that they differ in their susceptibility to iron-rich conditions. These observed differences correspond with differences in their respiration physiology, tolerance of poor oxygen conditions and overall life-history strategy documented in the literature. Our results exemplify how species can partition niche along a non-structural niche axis, such as sublethal iron-rich conditions. Other fish species may similarly segregate along concentration gradients in iron, while sublethal concentrations of other metals such as copper may similarly impact fish via respiratory impairment and reduced aerobic scope.

Despite the obvious negative effects caused by invasive species, some recent studies have shown that the impacts at local scale are diverse and not necessarily negative. Arborescent benthic organisms such as octocorals form three-dimensional structures capable of increasing the amount of substrate available and providing shelter for epibiont species. We investigated the role of the alien octocoral on the diversity of benthic communities in three shipwrecks on the north-eastern coast of Brazil. We expected that (a) the fauna associated with the octocoral are richer and more diverse compared to the adjacent; (b) some species are exclusively associated with ; (c) the species that are present both in the areas with and without have a greater abundance when associated with the octocoral. For this, we compared the macrobenthic communities associated with to those found in adjacent areas where the octocoral was absent. Our study showed that the communities associated with the octocoral were 1.5 times richer and 10 times more abundant than adjacent communities, with 29 exclusive taxa. The dominant taxa were the amphipods and and polychaetes of the family Syllidae. These taxa were present in areas with presence and absence of , but their abundance was significantly greater where the octocoral was present. Our results reinforce the idea that acts as an ecosystem engineer in coastal reefs, creating new habitats and increasing diversity at a local scale, even though it is an alien species.

To outline influence of anthropogenic activities on natural aquatic habitats such as wetlands, we sampled ostracods along with measuring several different aquatic variables at four different aquatic bodies between 2019 and 2020 in the Hıdırşeyhler Village (Bolu, Turkey). We found 15 living and 10 subfossil ostracods. Species with high tolerances () and/or with swimming abilities () were reported from the canal and wetland. Non-swimmer ostracods (e.g., ) were only found from the creek. Ostracod Watch Model illustrated some species with stenochronal and eurychronal (e.g., ) occurrences per site. CCA results displayed that water temperature and electrical conductivity were the most important explanatory variables on species. Unbiased diversity indices revealed the highest diversity in the canal followed by the creek, wetland, and trough. Wetland diversity exhibited positive and negative correlations with the canal and the creek, respectively. Tukey's pairwise test supported the significant comparisons between the trough, canal, and wetland ( < 0.01). The ratio of tolerant species per station was slightly higher in the canal than the wetland, trough, and creek. This suggests the fact that species encountered from the creek seem to be habitat specific and may be considered more vulnerable to changes in aquatic conditions. Frequency of species encountered in three habitats (wetland, canal, and trough) was significantly changed after the construction (digging and converting the wetland) activities began in August 2019. This activity was a negative impact on species diversity and richness in the wetland area where the diversity sharply dropped down and did not recover during the study. In contrast, this was probably advantage for some cosmoecious species.

Considerate the attitudes of traditional communities and their local ecological knowledge (LEK) can contribute to better policymaking and more appropriate management plans. Thus, this study strived to share the Minho River's fishermen LEK about great cormorant (Linnaeus, 1758), as well as it exposes their conservation attitudes towards this species. We described and analysed interviewees' LEK qualitatively, while their attitudes were analysed quantitatively through correlation with variables from fishermen's profile. Fishermen were able to identify cormorant's ecological characteristics like habitats, prey species, and foraging behaviour. They also exposed an overall moderate attitude towards the conservation of great cormorants. The LEK often was supported by published data, but we found diverse information in some themes, such as habitat and diet. We found a significant negative correlation between fishermen's age and attitudes ( = 0.02), and those fishermen who often fished contrasted significantly from those who rarely fished ( = 0.02). We lastly reaffirm the importance of the present study as background information regarding in Minho River and of ethnobiological studies as a tool for management plans.

In zooplankton surveys, many smaller taxa or species considered less important are often overlooked. One such example is the actinotrocha larvae of phoronid worms that are rarely quantified in zooplankton samples yet may play important roles in marine food webs. To gain a better understanding of phoronid ecology in coastal waters, we retrospectively analysed 145 plankton samples collected from two coastal sites in Ireland (Lough Hyne and Bantry Bay). Samples were collected using plankton nets from depths of 20 and 40 m. Phoronids were present in 37.7% and 38.2% of samples, with mean abundances of 0.3 ± 0.5 ind. m and 1.2 ± 2.8 ind. m, respectively, and were identified as and . Phoronids were present consistently each year from April to October at Lough Hyne and from February to October at Bantry Bay. Comparisons with other taxa in Lough Hyne show that abundances are similar to those of fish larvae (1.1 ± 1.8 ind. m) and echinoderm larvae (2.3 ± 4.4 ind. m). Examination of these samples from Irish waters suggests that phoronids are more abundant in temperate waters than previously reported.

Urban and agricultural expansion and intensification pose a critical threat to water quality and aquatic ecosystems. Increased nutrient loading into waterways combined with warming temperatures due to climate change have increased eutrophication and algal blooms. The relationship between land use, nutrient availability, and algal growth can vary dramatically across space and time, but few studies have captured this variation. The goal of this research is to assess water quality across time and disparate land uses, and its influence on algal community composition in the Albemarle Sound, a brackish water estuary in North Carolina. We collected water quality data from 21 sites across the sound, visiting six sites in Chowan County biweekly and 15 other sites twice between June and August 2020. Water samples from each site were tested for nitrate, phosphate, ammonia, bicarbonate, and total phosphorus (TP). Preserved algal samples from the six Chowan County sites were enumerated under a microscope to estimate genus richness and biomass. In the Chowan County sites, phosphorus increased and nitrate decreased over the course of the summer. Across all sites, TP increased with development and agricultural land use. These results suggest that sources of nitrogen and phosphorus in the sound differ. Algal richness increased with nitrate concentration and decreased with precipitation while biomass increased with water temperature. Our results indicate that climate change impacts, particularly increasing temperatures and extreme precipitation, influence how land use, water quality, and algal community composition interact. These data demonstrate the co-benefits of mitigating climate change in developing management strategies to reduce algal blooms.