Food Source For Fish Research Articles

Coral-seeding devices with fish-exclusion features reduce mortality on the Great Barrier Reef

Restoration methods that seed juvenile corals show promise as scalable interventions to promote population persistence through anthropogenic warming. However, challenges including predation by fishes can threaten coral survival. Coral-seeding devices with refugia from fishes offer potential solutions to limit predation-driven mortality. In an 8-month field study, we assessed the efficacy of such devices for increasing the survival of captive-reared Acropora digitifera (spat and microfragments) over control devices (featureless and caged). Devices with fish-exclusion features demonstrated a twofold increase in coral survival, while most corals seeded without protection suffered mortality within 48 h. Overall, spat faced more grazing and higher mortality compared to microfragments, and upward-facing corals were more vulnerable than side-facing corals. Grazing-induced mortality varied by site, with lower activity in locations abundant in mat-forming cyanobacteria or Scleractinian corals. Many scraping parrotfish were found feeding on or near the seeded corals; however, bites by Scarus globiceps explained the most site-related variation in grazing. Cyanobacteria may be preferred over corals as a nutritional resource for scraping parrotfish—advancing our understanding of their foraging ecology. Incorporating side-facing refugia in seeding devices and deploying to sites with nutrient-rich food sources for fish are potential strategies to enhance coral survival in restoration programs.

Spatial and temporal distribution of nutrients in the Ciliwung River, DKI Jakarta

The Ciliwung River, one of the largest rivers to run through Jakarta, is particularly important for its water quality because it travels through the city’s center and several settlements, highly populated housing areas, and slums. The growth of algae and macrophytes, or aquatic plants, is dependent on the nutrients in the streams. These plants serve as major food sources for fish and other small invertebrates. This study aimed to describe the distribution of nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River, DKI Jakarta, in terms of both space and time. Water quality was monitored under rainy (February and June 2021) and dry (August and September 2021) conditions. The research area, which included 18 observation stations, was situated in the DKI Jakarta sector along the Ciliwung River. Geographically, all river regions’ concentrations of total nitrogen, nitrate, and total phosphate exceeded the quality criteria; however, ammonia and nitrite tended to be high and did not meet norms across the Ciliwung River area, DKI Jakarta. While ammonia concentrations were greater during the dry season and nitrate concentrations were higher during the rainy season, there was a temporary difference in the concentrations of nitrite, total nitrogen, and total phosphate between the seasons.

Biofloc Technology (BFT) in Aquaculture: What Goes Right, What Goes Wrong? A Scientific-Based Snapshot.

Aquaculture is a crucial industry that can help meet the increasing demand for aquatic protein products and provide employment opportunities in coastal areas and beyond. If incorrectly manage, traditional aquaculture methods can have negative impacts on the environment and natural resources, including water pollution and overuse of wild fish stocks as aquafeed ingredients. Biofloc technology (BFT) may offer a promising solution to some of these challenges by promoting a cleaner and sustainable production system. BFT converts waste into bioflocs, which serve as a natural food source for fish and shrimp within the culture system, reducing the need for external inputs, such as feed and chemicals. Moreover, BFT has the potential to improve yields and economic performance while promoting efficient resource utilization, such as water and energy. Despite its numerous advantages, BFT presents several challenges, such as high energy demand, high initial/running costs, waste (effluent, suspended solids, and sludge) management, opportunistic pathogens (vibrio) spread, and a lack of understanding of operational/aquatic/microbial dynamics. However, with further training, research, and innovation, these challenges can be overcome, and BFT can become a more widely understood and adopted technique, acting as an effective method for sustainable aquaculture. In summary, BFT offers a cleaner production option that promotes circularity practices while enhancing performance and economic benefits. This technique has the potential to address several challenges faced by the aquaculture industry while ensuring its continued growth and protecting the environment. A more broad BFT adoption can contribute to meeting the increasing demand for aquaculture products while reducing the industry's negative impact on the environment and natural resources. In this context, this review provides an overview of the advantages and challenges of BFT and highlights key technical, biological, and economic aspects to optimize its application, promote further adoption, and overcome the current challenges.

Effect of Physico-Chemical Parameters and Inorganic Nutrient Ions in Relation with Seasonal Algal Diversity of River Ichhamati, West Bengal, India.

The present study reflects seasonal algal diversity as a source of food for fishes in the river Ichhamati during October 2021 to August 2022. To understand the seasonal algal pattern in the river Ichhamati, physicochemical parameters of river water such as Hardness, Conductivity, pH, Total Dissolve Solids, Turbidity, Dissolve Oxygen, Salinity, Turbidity, Total Alkalinity, Salinity, Biological Oxygen Demand as well as biologically significant inorganic ion concentrations in river water namely sodium, potassium, calcium, carbonate, bicarbonate, nitrate, chloride were also evaluated during study period. It is found that physico-chemical parameters and inorganic ions in river water play an important and significant role in seasonal algal growth. Throughout the study period it was established that river Ichhamati is not very rich in floral diversity. During study time it was observed that dominant group of algae in this river are Chlophytes, Cyanophytes and Bacilariophyceae, including Species of Oscillatoria Nostoc, Klebsormidium, Spirogyra, Lyngbya, Chlorococcum, Chlorella, Diatoms in all seasons. During spring, summer and monsoon Conductivity, salinity, TDS and hardness of river water is high. Ichhamati contained adequate Na+, K+ and NO3- in summer and monsoon season. High rate of bio-mineralisation during winter was found due to presence of high calcium ion concentration and also high TDS along with high salinity as well as high hardness of river water.

Pilot Lipidomics Study of Copepods: Investigation of Potential Lipid-Based Biomarkers for the Early Detection and Quantification of the Biological Effects of Climate Change on the Oceanic Food Chain.

Maintenance of the health of our oceans is critical for the survival of the oceanic food chain upon which humanity is dependent. Zooplanktonic copepods are among the most numerous multicellular organisms on earth. As the base of the primary consumer food web, they constitute a major biomass in oceans, being an important food source for fish and functioning in the carbon cycle. The potential impact of climate change on copepod populations is an area of intense study. Omics technologies offer the potential to detect early metabolic alterations induced by the stresses of climate change. One such omics approach is lipidomics, which can accurately quantify changes in lipid pools serving structural, signal transduction, and energy roles. We utilized high-resolution mass spectrometry (≤2 ppm mass error) to characterize the lipidome of three different species of copepods in an effort to identify lipid-based biomarkers of copepod health and viability which are more sensitive than observational tools. With the establishment of such a lipid database, we will have an analytical platform useful for prospectively monitoring the lipidome of copepods in a planned long-term five-year ecological study of climate change on this oceanic sentinel species. The copepods examined in this pilot study included a North Atlantic species (Calanus finmarchicus) and two species from the Gulf of Mexico, one a filter feeder (Acartia tonsa) and one a hunter (Labidocerca aestiva). Our findings clearly indicate that the lipidomes of copepod species can vary greatly, supporting the need to obtain a broad snapshot of each unique lipidome in a long-term multigeneration prospective study of climate change. This is critical, since there may well be species-specific responses to the stressors of climate change and co-stressors such as pollution. While lipid nomenclature and biochemistry are extremely complex, it is not essential for all readers interested in climate change to understand all of the various lipid classes presented in this study. The clear message from this research is that we can monitor key copepod lipid families with high accuracy, and therefore potentially monitor lipid families that respond to environmental perturbations evoked by climate change.

Hierarchical Interaction between Food Diversity and Competition in Brackish Fish Species in South Korea

Information about the food sources for fish is important not only for predation and food competition, but also for the direct impact on organism interactions, relationships, and biodiversity within aquatic ecosystems. We analyzed the food sources of 21 fish species in 9 families of 6 orders based on the literature data from brackish ecosystems in South Korea to improve the understanding of the estuarine ecosystem. The food sources of the 21 fish species contained 173 families, 86 orders, 39 classes, and 22 phyla. The 21 fish species were classified into 4 groups using hierarchical analysis based on their food sources: Group 1 fishes mainly consumed Amphipoda; Group 2 fishes were zooplanktivores; Group 3 were omnivorous; and Group 4 consumed small food sources, such as Nematoda, Corophiidae, and Harpacticidae. The feeding competition index was relatively high within each group, but the competition index for Group 3, the omnivorous fishes, was low. Network analysis and hub scores represented the importance of food sources consumed by each fish species by showing the connections between the fish and their prey. Polychaeta, Actinopterygii, and Decapoda were the most commonly consumed food sources. Food source diversity was high for zooplanktivores (group 2). Additionally, the food contents of each fish species were classified into freshwater and marine sources for identifying the habitats of the food sources. Trophic level measuring values using the data were similar to the reported literature data. This study can be utilized for understanding estuarine ecosystems and identifying food relationships.

Investigating food web structure and system function of an artificial reef ecosystem based on carbon and nitrogen stable isotope analysis: implications for reef management

IntroductionFood web is an important basis for identifying trophodynamic processes, and evaluating the structural and functional characteristics of ecosystems. The trophodynamics and system function of artificial reef (AR) ecosystems have rarely been examined.MethodsStable isotope analysis was used to investigate the food web structure and functions of an artificial reef (AR) ecosystem in this study.Results and DiscussionThe δ13C and δ15N values of particulate organic matter (POM) in AR showed noticeable seasonal changes, and the δ13C value of POM in autumn was significantly higher than that in other seasons (p<0.05). There were no significant seasonal variations in the δ13C values of solid organic matter (SOM), and no significant difference between SOM and POM was observed except in autumn. Moreover, macroalgae did not significantly affect the δ13C values of SOM. Phytoplankton may be the primary nutrient source in the AR ecosystem. The δ13C values of most crustaceans in the AR were approximately between (-17.03 ± 0.22) ‰ – (-17.74 ± 0.07) ‰, higher than those of most fish, indicating that they may have different basal nutrient sources. The trophic level (TL) of invertebrates was between 2.00 and 3.09, and that of fish was between 2.98 and 3.66. The distribution of δ13C and TLs of crustaceans and fish showed that, except for crustaceans, bivalve shellfish and zooplankton might also be important food sources for fish in the AR ecosystem.ConclusionThe δ13C and δ15N values of most species in the AR showed good continuity, indicating that they may be mainly produced from the AR ecosystem. Migratory species such as Lateolabrax japonicus and Sepiella maindroni showed higher δ13C values, indicating that they may have migrated from other sea areas. To maintain the stability of the ecosystem structure and function of the AR ecosystem, fishing activities should be carried out following the maximum sustainable yield theory. Future research needs to identify the nutritional relationship between AR and its adjacent sea areas, to depict the food web structure of the AR with higher accuracy.

Comparative study of algal community in African sharptooth catfish (Clarias gariepinus, Burchell 1822) and Nile tilapia (Oreochromis niloticus, Linnaeus 1758) farming ponds

AbstractIn subsistence and small‐scale fish farming, algae are an important food source for fish. Therefore, understanding their distribution and diversity in fish ponds is essential. This study aimed at characterising algae species in African sharptooth catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) farming ponds and their contribution to these species’ diet. Water samples were collected from different points of the farming pond: in rearing pond, evacuation canal of each species and decantation pond. Samples were also collected from fish stomachs and intestines. Afterwards, they were analysed with a photonic microscope for species identification using standard identification keys. The highest species richness (S) and Shannon index (H) were observed in fish rearing ponds (S = 73, H = 2.98–3.84) and the lowest in fish stomachs and intestines (S = 41, H = 1.88‐3.07). Jaccard's similarity index, ranging from 0.17 to 0.55, shows a high specific diversity of alga in the different sampling points. During the experimental period, water physicochemical parameters were within the optimum growth for algae and fish species. Since some algae species recorded are consumed by both fish species, this study recommends to select and cultivate them for fish food production.

Differential distribution of macroinvertebrate associated with water quality

AbstractStreams and rivers are the major source of drinking water and irrigation in many developing countries. Stream health is a major criterion and regulator of the health of its dependents (invertebrates, aquatic flora, fishes, animals, and humans). For the sustenance of a balanced ecosystem, a mutual existence between flora and fauna along with other abiotic factors is a prerequisite. Benthic fauna lying on the riverbed serves as a food source for fish, larger insects, birds, etc. Nowadays, most freshwater bodies are getting polluted through various anthropogenic activities like mining, land‐use practices (fertilizers and insecticides), industrial effluent, and sewage inlet. Due to the water contamination, there have been observed changes in the physicochemical parameters of the water. The macroinvertebrate species being sensitive to these changes play an important role not only in determining the health of the water body but also in regulating the ecosystem. After review, it was observed that order like Diptera dominated in various locations, comprising of family Ceratopogonidae and Chironomidae, followed by order Trichoptera and Coleoptera. Species belonging to family Baetidae and Chironomidae possess pollution tolerance capabilities; additionally, these species can survive at a wide range of temperatures. Species from families such as Simuliidae showed their existence at varying water velocities. Families like Limnephilidae, Simuliidae, and Glossosomatidae exhibited their survival in fast moving water whereas Notonectidae, Hydrophilidae Gomphidae, Coenagrionidae, Libellulidae, Aeshnidae, and Dryopidae indicated species of low waterflow. Species of the family Tipulidae have been related to areas of high conductivity, whereas Gomphidae, Dryopidae, and Glossomatidae as species of low conductivity. Hydrophilidae and Notonectidae dominated high temperature areas. The present study will put forth before the government, current scenario of macroinvertebrate structure depending on the different characteristics of the water. This will help in regulating and controlling water pollution.

Gastropod Microhabitat Associations and Niches in Seagrass Ecosystems on Donrotu Island, South Jailolo District, West Halmahera Regency

Gastropods are included in the mollusk phylum which is known to be well-associated with seagrass ecosystems. The gastropod community is an important component in the food chain in seagrass beds and ecologically seagrass beds have an important role in the ecosystem. Seagrass ecosystems are habitats and food sources for fish and other aquatic biota. One of the biota commonly found in seagrass beds is Gastropods. This study was conducted to know the composition of gastropod species, types of gastropod associations, and gastropod microhabitat niches in seagrass ecosystems on Donrotu Island. Gastropod sampling was carried out at low tide. The gastropod samples found were then put into a plastic bag that already contained a label. Furthermore, the gastropod samples were brought ashore to count the number of individuals of each type and determined based on morphological characteristics such as shell shape, shell color, shell mouth opening, and spiral circle based on Dharma (1992) instructions. Based on the results of the study, the composition of the types of gastropods found in the seagrass ecosystem on the island of Donrotu was as many as 13 species. There were 13 pairs of gastropod types that had positive associations and 65 pairs of no associations. The type of gastropod that has the widest habitat niche is Cypraea tigris and the narrowest are Naticarius coillei and Pseudovertagus aluco.

Analisis densitas Zooxanthella pada karang Acropora sp di Perairan Pulau Talam Tapanuli Tengah Provinsi Sumatera Utara

Coral reefs are a unique ecosystem of tropical waters that have physical function as a beach protector with its nature that can reduce the energy of waves moving towards the coast. Coral reef ecosystems are a good places for spawning, nurturing and food sources for fish. The aim of this research was to determine the density of zooxanthella on coral Acropora sp based on different depths. The method that used in this research was a survey method by taking coral samples using purposive sampling technique, then the samples were analyzed and the data was discussed descriptively at the Marine Biology Laboratory, Faculty of Fisheries and Marine, Riau University. The results of this research on the waters of Talam Island obtained a brightness up to 100% of depth, a current velocity was 0.05–0.10 m/s, temperature ranging from 30-32 0C, salinity of 34 o/oo and pH ranging from 7.2–7.6. The corals that used as research objects for zooxanthella density were taken at a depth of 3 m, 5 m, and 7 m, namely the coral Acropora sp. The results showed that the average zooxanthella density on Acropora sp coral at a depth of 3 meters was 6.35x106 cells/cm2, a depth of 5 meters was 2.63x106 cells/cm2, and 1.95x106 cells/cm2 at a depth of 7 meters. Based on observations, the density zooxanthella was decreased by increasing depth.

Experimental Study on the Impact of Pulsed Flow Velocity on the Scouring of Benthic Algae from a Mountainous River

The decrease in periodic scouring of pulsed flows in regulated rivers can result in algal communities dominated by filamentous algae, not available as food sources for fish and macroinvertebrates. To study the pulsed flow velocity required to scour benthic algae from natural river beds, the removal effects on the algal biomass and resistances of different species were tested in a laboratory flume at different velocities of 0.8, 1.1, 1.4, 1.7, and 2.0 m/s. The removal of total algal biomass showed a significant positive relationship with increasing velocities, which reached 22% at 2.0 m/s. The biomass removal of green algae and diatoms was higher than that of blue–green algae. The flow velocity at 1.4 m/s had a clear removal effect on filamentous algae. The velocity higher than 1.7 m/s caused a significant increase in the removal percentage of total biomass dominated by diatoms and blue–green algae. To reduce the filamentous algae and retain the diatoms and blue–green algae, a range of near bed flow velocity was suggested to be 1.4–1.7 m/s. This range could serve as a reference for required pulsed flow velocity to reduce the growth of excessive or nuisance periphyton.

Juliana Lake: A Wetland in an Urban Environment1

Of all the remaining natural habitats of Benghazi’s urban area (NE Libya), perhaps the most threatened are its karst lakes and coastal salt marshes (locally known as Sebkha). Juliana Lake stands out as one example of a fragile ecosystem that is steadily shrinking and exposed to dredging, infilling and, consequently, possible damage to its aquatic organisms, and the inevitable loss of its renowned biodiversity. Several 19th & 20th–century traveller’s sketches and maps, soil maps, photographs and satellite images provide the bases for change in the size and magnitude of the lake and its adjacent areas over time. Assessment of the sediment composition and texture of material accumulating at the bottom of the lake reveals mixtures of Sebkha sediments such as salty clay, silt, and clayey sand, while sediments at the surface and around the lake are represented by quite soft whitish to yellowish and scattered patchy limestones of unknown affinity. Terra-rossa and Quaternary caliche are present also, but calcarenites cover considerable part of the studied area. The bio-micro components of these sediments are described and a number of small-sized benthic foraminifera have been identified. Macrofauna, which are primarily presented by recent benthic seashells belonging to phylum mollusca, have also been investigated and several species have been identified to the species level wherever possible. Other calcareous biotic components are predominantly shell fragments of molluscs, echinoderms and calcareous coralline red algae. It is concluded that the distribution, diversity and abundance of the total benthic organisms recovered in this survey reflect the habitat's richness in nutrients and consequently providing important food source for fish, birds, and mammals. It is argued that environmentally based planning strategies can preserve the fragile landscapes of Benghazi and, furthermore, ensure a more sustainable form of future urban development. In this context, urban planners should review routine urban planning practices affecting Juliana wetland and other natural landscapes of Benghazi, and adjust them to integrate nature into the urban scene of current and future development plans.

Interactions between Fish and Invertebrates in the Lowland Area of the Sava River following Excessive Change in Hydrological Regime

The littoral zones of freshwaters are highly susceptible to extreme hydrological fluctuations caused by climate-induced changes in the water cycle. Disturbances in the hydrology could affect fish assemblages and their trophic interactions with invertebrates, which constitute a large part of fish diets. In 2014 and 2015, the littoral zone of the Sava River (Croatia) was studied to determine the influence of hydrological extremes on (1) fluctuations in environmental drivers and biocoenoses, and (2) the trophic relationships between fish, macroinvertebrates and zooseston, in an attempt to reveal their trophic interactions. Biocoenotic components showed different tolerance to extreme discharge, resulting in remarkable reductions in fish abundance, diversity, biomass, size and, presumably due to dilution, the abundance of zooseston, which is an important food for fish larvae. By contrast, benthic macroinvertebrates did not show significant fluctuations in abundance, but the share of benthic groups of organisms was shifted during high discharge. Gastropods and amphipods were found to be important food sources for fish. The present study helps to highlight the consequences of hydrological disturbances caused by climate change: the enhancement of stressors in riverine littoral habitats and inhabited communities.

Trophic transfer of lipids and fatty acids across habitats in tropical river food webs

Abstract Polyunsaturated fatty acids (PUFA) are essential components of cell membranes and reproductive and sensory organs in vertebrates and are largely acquired through their diets. Accordingly, identification of the dietary sources of PUFA is an important consideration in food web studies. We collected fish, macroinvertebrates (aquatic and terrestrial), and plants (aquatic and terrestrial) from floodplain and river channel habitats in a tropical river catchment in northern Australia, to identify food sources and habitats that provided lipid and PUFA rich food that sustain fish populations. The composition of most FA in fish was similar to that reported from other freshwater tropical environments, with the exception of their higher arachidonic acid content. Fish were found to derive their fatty acids primarily from aquatic sources of food and had similar FA composition to aquatic macroinvertebrates. Aquatic macroinvertebrates fed on aquatic plants (algae) and had higher total lipids and FA contents than plants and fish, providing a more concentrated source of PUFA for fish. Fish obtained most of their FA from their diet except for docosahexaenoic acid (DHA), which they must synthesize due to low DHA in algae and macroinvertebrates. There was no overall difference in basal dietary FA composition between floodplain and river channel habitats. However, macroinvertebrate taxa varied in their lipid and PUFA content. Food quality for fish may therefore vary between habitats as a consequence of differences in macroinvertebrate community composition. Given the high algal production on floodplains compared to the river channels, these habitats are likely to represent the major source of high quality food for fish and other aquatic consumers, and conserving habitats that are rich in lipids and PUFA is important for maintaining healthy fish communities.

Chlordecone-contaminated epilithic biofilms show increased adsorption capacities

The rivers of Guadeloupe and Martinique (French West Indies) show high levels of chlordecone (CLD) contamination. This persistent molecule has a dramatic impact on both aquatic ecosystems and human health. In these rivers, epilithic biofilms are the main endogenous primary producers and represent a central food source for fish and crustaceans. Recently, their viscoelastic properties have been shown to be effective in bio-assessing pollution in tropical environments. As these properties are closely related to the biochemical composition of the biofilms, biochemical (fatty acids, pigments, extracellular polymeric substances (EPS) monosaccharides) and molecular markers (T-RFLP fingerprints of bacteria, archaea and eukaryotes) were investigated. Strong links between CLD pollution and both biofilm biochemistry and microbial community composition were found. In particular, high levels of CLD were linked with modified exo-polysaccharides corresponding to carbohydrates with enhanced adsorption and adhesion properties. The observed change probably resulted from a preferential interaction between CLD and sugars and/or a differential microbial secretion of EPS in response to the pollutant. These changes were expected to impact viscoelastic properties of epilithic biofilms highlighting the effect of CLD pollution on biofilm EPS matrix. They also suggested that microorganisms implement a CLD scavenging strategy, providing new insights on the role of EPS in the adaptation of microorganisms to CLD-polluted environments.

Large conservation opportunities exist in >90% of tropic-subtropic coastal habitats adjacent to cities

Large conservation opportunities exist in >90% of tropic-subtropic coastal habitats adjacent to cities

Zooplankton (Cladocera and Copepoda) in Cajititlán Lagoon

Cladocerans and copepods are the main zooplankton formers in freshwaters. The actual state of pollution faced by the lagoon of Cajititlán restricts the amount of species able to habit this water body, and with it, the functionality of the ecosystem due to their role as phytoplankton consumers and as the principal food source for fishes and other organisms. Until now, there was very little knowledge about these groups in the lagoon, which is because of the lack of specialists in the occidental region of Mexico and the inherent difficulties with respect to the manipulation of these organisms (their size round between 0.2 to 4 mm, besides, manual dissections must be done in order to observe taxonomic characters). In this study, we analyze the composition and abundance of the zooplankton in Cajititlán Lagoon focused in both groups (Cladocera and Copepoda). To achieve this objective, five sites within the lagoon were chosen based on their position with respect to the principal human populations. Samples were collected using a plankton net of 63 μm mesh light with one horizontal tow-in each site monthly. The analyzed period comprehends from May 2015 to April 2016, completing an annual cycle. Each sample was fixed using 4 % formaldehyde. Organisms were first identified the species level and their abundance was calculated with manual counts using a Bogorov chamber. Six species were recorded: Daphnia ambigua and Diaphanosoma birgei (Cladocera) and Arctodiaptomus dorsalis, Leptodiaptomus siciloides, Mesocyclops edax and Neoergasilus japonicus (Copepoda). The most abundant and frequent species was A. dorsalis, followed by M. edax and D. ambigua. Leptodiaptomus siciloides and N. japonicus appeared to be rare species, but L. siciloides was very abundant in March and April. The most abundant species was A. dorsalis, occurring nearly in 77 % of the samples and an average of 5 organisms per liter (up to 60 org/l), while the most frequent was M. edax, with up to 87 % of occurrences and an average of 3 org/l (up to 80 org/l). The general abundance of both groups in this water body was below and the species composition corresponds to the expected in an eutrophicated waterbody.

Upstream flows drive the productivity of floodplain ecosystems in tropical Queensland

Rivers in tropical systems across the world are well known for their strong connections with floodplain wetlands. However, increased water needs and changing climate could drive water-management policy that leads to major changes in flow or surface water availability. These changes could have deleterious effects on ecological functions and ecosystem services provided by these freshwater ecosystems (e.g., groundwater recharge, food sources for fish, etc.). In this study, we introduce a cloud-based monitoring framework using multi-resolution satellite observations (2007-2020), historical surface inundation (1984-2015), and gauge data to better understand these connections in a large river catchment in tropical Queensland (Mitchell River catchment). A key driver and indicator of floodplain productivity, surface water inundation and aquatic biomass distribution respectively, are investigated to provide insight that underpins the prioritization of future surface water developments in this region. Results show that the characteristics of floodplain inundation; loss, persistence, gain and frequency, vary in time and space, and are driven by climate variability. The largest gain (7200 Ha) and persistence (8437 Ha) in total surface inundation were observed in the wet seasons during the periods of 2007-2019, respectively. In the downstream catchment, permanent water surface area was approximately 4.5% (of the total downstream region) compared to the upstream region (2.7%). There is a higher proportion of new permanent water features (16.8%) and new seasonal (30%) surface water classes in the upstream are in contrast to the downstream section (0.7% and 9.6%, respectively). Using multivariate statistics, floodplain productivity was linked to inter-annual changes in flow and rainfall. A partial least squares regression (PLSR) model shows upstream flows drive changes in total floodplain inundation (observed vs predicted, r=0.95,p=0.000). Flows and local rainfall accounted for approximately 60% (r=0.77,p=0.005) and 25% (r=0.50,p=0.120) of the variability in total floodplain inundation, respectively. Different PLSR modelling scenarios confirmed that upstream flows are primary drivers of floodplain inundation and substantial lost in total surface inundation could happen if flows are altered. Just as local rainfall has limited impact on total floodplain inundation (r=0.92,p=0.000; for model excluding local rainfall), aquatic plant biomass accumulations are also strongly associated with upstream flows (e.g., r = 0.82). Given the dependence of downstream water level (r = 0.89) and floodplain inundation on upstream flows, sustainable management of river flows in the Mitchell River is fundamentally important to floodplain productivity.

Carcass deposition to suppress invasive lake trout causes differential mortality of two common benthic invertebrates in Yellowstone Lake

Invasive species require management to mitigate their harmful effects on native biodiversity and ecosystemprocesses. However, such management can also have negative, unintended consequences on non-target taxa,ecosystem processes, and food web dynamics. In Yellowstone Lake, invasive lake trout (Salvelinus namaycush)have caused a decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) population. Tosuppress the invader, lake trout carcasses are deposited on the species’ spawning sites, causing embryo mortalityby reducing dissolved oxygen as they decay. The non-target effects of carcass deposition are unknown, but benthicinvertebrates may be sensitive to reductions in dissolved oxygen. Benthic invertebrate taxa have varying hypoxiatolerances; caddisflies of the family Limnephilidae are hypoxia sensitive whereas the amphipods Gammarus lacustrisand Hyalella azteca are hypoxia tolerant. Both taxa are widespread and abundant in Yellowstone Lake andcomprise a large proportion of fish diets, and changes in their abundances could therefore alter food web dynamics.We conducted an in situ experiment to determine if carcass deposition causes mortality in these two benthic invertebratetaxa. The probability of mortality for caddisflies was 3.15 times higher in carcass treatments compared tocontrols, while amphipod mortality did not change in response to carcass treatment. Amphipods, which contributemost significantly to fish diets, are unlikely to be reduced in response to carcass deposition, which is confined to asmall fraction of the lake where lake trout spawn, limiting the possibility for lake-wide effects. We conclude thatcarcass deposition is unlikely to alter the availability of invertebrates as a food source for fish in Yellowstone Lake.