The Ciénaga Grande de Santa Marta, located in the Department of Magdalena, forms the Estuarine Delta System of the Magdalena River and extends to the Caribbean Sea. Its ecosystem assets include the largest mangroves in the Colombian Caribbean, continental wet areas, coastal lagoons, forests, agricultural and transformed land types. The site supports fisheries and agriculture and provides carbon storage, habitat and other services to local communities. It also carries a series of overlapping conservation designations, including a flora and fauna sanctuary, a biosphere reserve, an important bird area, the Salamanca Island Park and Ramsar status. The Ramsar designation dates to 1998.

The wetland’s condition depends on the interaction between freshwater and seawater throughout the year. This exchange shapes water salinity, while changes in river flow alter the salinity of mangrove soils and influence both vegetation and fisheries. Diversion of water from rivers descending from the Sierra Nevada de Santa Marta for agriculture, together with construction of the Barranquilla–Ciénaga and Palermo–Sitio Nuevo roads, has altered exchange inlets and reduced connectivity between the Magdalena River and the lagoon complex. An integral environmental recovery program initiated by INVEMAR in the 1990s included dredging a five-channel network to restore water exchanges among the Magdalena River, lagoon bodies and the Caribbean Sea. Monitoring of the resulting hydrological regime continues, with hydro-sedimentological observation beginning in 2017.

These pressures complicate an ecosystem already affected by climatic variability. Strong and very strong El Niño events in 2015 and 2016 were associated in the study with reduced rainfall in the Colombian Caribbean, increased mangrove-soil salinity and hydrological stress. In 2017, a Ramsar advisory mission found strong changes in the wetland’s ecological characteristics associated with water-balance loss and human intervention, leading to its inclusion in the Montreux Record. The new study combined environmental and socioeconomic data into a spatial account intended to show how changes in ecosystem extent and condition affect the supply of services and the associated economic value.

For the extent account, researchers compared two CORINE Land Cover layers mapped at a scale of 1:100,000, representing 2012 and 2018. They standardized the land-cover classifications, calculated geodesic areas and used spatial intersections to construct a transition matrix showing opening extent, gains, losses and closing extent. Pastures, continental wet areas and mangrove forests recorded the largest losses during 2012–2018, while permanent crops, heterogeneous agricultural areas and areas with herbaceous or shrub vegetation recorded the largest gains. Mangroves, continental wet areas and pastures mainly transitioned into agricultural or transformed-cover classes. The analysis identified where losses occurred but could not attribute each gain or loss to a specific natural event or human action.

Condition accounts were possible only for mangroves and coastal lagoons and covered 2017–2019 because of data availability. The framework classified condition variables under abiotic, biotic and landscape characteristics. Mangrove indicators included basal area, seedling and propagule density, interstitial salinity, bird species richness and change in extent related to water. Coastal-lagoon indicators included dissolved oxygen, total suspended solids, surface salinity and fish species richness. Reference levels drawn from monitoring reports, regulatory criteria, bibliographic sources and observed salinity ranges were used to rescale variables and construct aggregate condition indices.

The two monitored ecosystem types showed different trends. Mangrove condition had a net positive change from 2017 to 2019 because abiotic values rose as interstitial salinity declined, biotic values rose with greater bird richness and more seedlings and propagules, and landscape values improved as mangrove area expanded. Basal area decreased during the period, showing that recovery was not uniform across every measured characteristic. Coastal lagoons recorded a net negative change: dissolved oxygen declined, surface salinity increased and fish species richness fell. The contrasting aggregates demonstrate how condition accounting can distinguish environmental improvement in mangrove forests from deterioration in adjacent lagoon waters.

Mangrove extent increased by 3,503 hectares during 2017–2019, equivalent to a reported recovery of 6.87% relative to the 51,150 hectares recorded in 1956. The researchers associated this increase with freshwater inflows through dredged channels connected to the Magdalena River and with the absence of El Niño-related events during part of the accounting period. Bird richness also increased, with 98 species recorded in 2019. The list included the northern screamer, sapphire-bellied hummingbird and bronzed cowbird, together with numerous migratory species. These observations describe improvement within the selected indicators and period; they do not establish that every component of the lagoon complex recovered.

Fishing-resource data showed how environmental variation appeared in a service used by communities. SIPEIN records showed total artisanal catch ranging from 4,617 to 6,035 tonnes per year between 2015 and 2019, a net difference of 721 tonnes per year between the opening and closing years. Fish contributed the largest catches, followed by crustaceans. Mollusc catches were not collected in 2018–2019 because of logistical problems, so the reported total underestimates those resources in those years. Catch fell sharply in 2016, coinciding with the highest salinity records in two decades, and subsequently recovered as salinity declined and the composition of the fishery shifted among estuarine, marine and freshwater species. The account therefore documents an association between salinity, climate variability and recorded catches rather than isolating the contribution of any one factor.

The climate-regulation account focused on mangrove carbon. Aboveground carbon was estimated from tree diameter and biomass relationships, while belowground estimates were drawn from measurements covering the upper metre of soil. Carbon stocks were valued using Colombia’s carbon tax rate, set at USD 5 per tonne of carbon dioxide in 2017 with annual adjustment. Aboveground carbon content declined across the principal mangrove types over 2015–2019, leaving total mangrove carbon 16.5% lower in 2019 than in 2015. Most of the decline occurred between 2015 and 2017, when mangrove loss, hydrological stress, desiccation and charcoal burning were associated with carbon emissions rather than sequestration. Physical carbon stocks rose during 2018 and 2019, but their monetary value declined as the Colombian peso depreciated against the dollar. Soil-carbon estimates are incomplete because the reference measurements covered only one metre, while mangrove carbon reservoirs extend deeper.

The monetary asset account placed the value of mangrove carbon stocks at USD 68.3 million in 2015 and USD 55.13 million in 2019. Annual wild-fish supplies from mangroves and coastal lagoons were converted to asset values using a net-present-value method with a 100-year asset life and a 3.5% social discount rate. The combined mangrove and coastal-lagoon asset estimate was USD 105.71 million in 2015 and USD 97.27 million in 2019. The resulting difference of USD 21.61 million comprised USD 13.17 million in mangrove losses and USD 8.44 million in losses for the combined coastal-lagoon and mangrove category. These are accounting estimates, not observed losses of cash or conventional market assets. They provide a way to place ecosystem assets and service flows on the same statistical framework as economic activity.

The pilot also exposes important constraints. Catch is recorded at four landing places and distributed across the wetland, rather than assigned to the specific mangroves, lagoons or marine areas that produce it. This prevents precise attribution of fishing benefits within an interconnected coastal landscape. The condition accounts do not include all six classes in the SEEA EA condition typology, and the land-cover transition analysis cannot determine whether individual changes resulted from El Niño, farming, infrastructure or another pressure. Fishers’ income also cannot be inferred from physical catch alone because market prices, price elasticity, consumer preferences and pre-sales arrangements affect the revenue received. Even with those limitations, the account establishes a baseline for monitoring the extent, condition and service flows of a Ramsar wetland and offers Colombia a spatial framework for integrating ecosystem information into environmental statistics, biodiversity reporting and economic planning.

Subject of Research: Pilot ecosystem accounting of Colombia’s Ciénaga Grande de Santa Marta Ramsar Site

Article Title: Accounting of marine and coastal ecosystems at the Ramsar Site, Estuarine Delta System of the Magdalena River, Ciénaga Grande de Santa Marta, Colombia

Article References: Gomez Cardona, C., Moreno, J., Contreras, A., Sanchez-Nuñez, D., Arciniegas Moreno, N., Guerrero, D., Viloria Maestre, E., & Lopez Navarro, J. (2023). Accounting of marine and coastal ecosystems at the Ramsar Site, Estuarine Delta System of the Magdalena River, Ciénaga Grande de Santa Marta, Colombia. One Ecosystem, 8, Article e98852. https://doi.org/10.3897/oneeco.8.e98852

Image Credits: AI Generated

DOI: 10.3897/oneeco.8.e98852

Keywords: Ciénaga Grande de Santa Marta, ecosystem accounting, SEEA EA, mangrove carbon, coastal lagoons, artisanal fisheries, wetland condition, natural capital, El Niño, Ramsar Site, Accounting, marine

The reason this single record matters so much lies in a stubborn asymmetry of sea turtle biology. Nesting females are, in a sense, the easiest turtles in the world to study. They haul themselves onto beaches in predictable numbers, dig conspicuous nests, and obligingly present themselves to teams of researchers who count, measure, and tag them season after season. Males never come ashore. Once hatchlings reach the sea, male sea turtles may not touch land again for decades, remaining fully aquatic and eluding the beach-based monitoring programs that have generated nearly everything science knows about sea turtle demography. As a result, adult males are among the least studied segments of any sea turtle population, and basic questions about where they live, how long they stay near breeding grounds, how often they return to mate, and how many reproductively active males are available in a given season remain largely unanswered, especially for hawksbills in the Caribbean.

Those questions are not academic curiosities. The number and availability of reproductively active males during a breeding season determine what ecologists call the operational sex ratio, a measure of the ratio of fertilizable females to sexually active males in a population. The operational sex ratio shapes mating competition, influences reproductive success, and feeds directly into estimates of population viability. Male behavior also underpins gene flow and patterns of multiple paternity, which have been documented in marine turtles through genetic studies showing that females may mate with several males across a season. If males are scarce, or if they visit breeding areas only intermittently, the reproductive output of a rookery could be affected in ways that female-focused nesting counts would never reveal. Understanding males is therefore essential to managing populations, particularly in key regions such the Caribbean Sea, where the hawksbill, a critically endangered species, still nests on scattered beaches.

The Gulf of Paria is exactly the kind of place where such knowledge is needed. Its hawksbill rookery ranks as the second largest for the species in the southern Caribbean Sea, yet it has shown worrying nesting declines in earlier assessments, raising questions about the population’s long-term prospects. Venezuelan sea turtle research has historically concentrated on nesting females, whether leatherbacks on the Paria Peninsula, green turtles at Aves Island, or the hawksbills of the Gulf of Paria itself. In-water research, the approach that can actually reach males, has been almost entirely absent from the country; the only comparable neritic study to date focused on hawksbill habitat in Los Roques Archipelago National Park. Against that backdrop, a team led by Clemente Balladares of Universidad Central de Venezuela, together with Marco Garcia-Cruz, José Alio, and Hector Barrios-Garrido, set out in April 2023 to gather whatever preliminary data they could on adult male hawksbills near the rookery, publishing their findings in Frontiers in Amphibian and Reptile Science.

Their method combined two deliberately separate sampling streams. The first was researcher-led: stationary net hauls conducted roughly every two weeks off Los Garzos Bay, adjacent to the main nesting beach. Each net, measuring 100 meters long by 10 meters deep with a fine 15-centimeter mesh, was set perpendicular to the coastline about 50 meters offshore in water 4 to 12 meters deep, and each two-hour haul began after sunrise, between 5 and 7 in the morning. Of 40 planned hauls, 33 were completed between April 2023 and November 2024, with the rest cancelled by rough seas or drifting Sargassum mats, yielding 60 hours of effective sampling effort. The second stream was fishery-dependent: from September 2023 to June 2025, trained local assistants validated reports from artisanal fishers landing their catch near Aricagua Bay, Calera, and the Las Garcitas Islets, recording species, measurements, photographs, gear type, tag numbers, and the condition of any turtles caught incidentally. The two datasets were never pooled, because their designs, effort levels, and detection probabilities differ too much to support combined analyses of abundance or residency.

Every captured turtle was brought aboard, disentangled, measured for curved carapace length and width, checked for injuries and buoyancy problems, and kept shaded and wet to minimize stress. Sexing an adult male relies on a visible anatomical signal: the tail of a mature male grows long enough to extend well beyond the rear edge of the carapace, a secondary sexual characteristic absent in females and juveniles. Turtles without tags received new Inconel tags on both front flippers, and photographs of carapace, head, and tags were taken before release to support future photo-identification. The research-led surveys captured nine turtles in total, six juvenile green turtles, one adult male green turtle, and two adult male hawksbills, for a capture rate of 0.15 turtles per hour. Meanwhile, the validated fishery records documented 15 incidental captures involving three gear types: stationary nets, single hooks, and a 250-meter longline, with stationary nets accounting for most reports.

The headline result came from one of those two male hawksbills. Tagged as V001M and V002M on 26 June 2023 in Los Garzos Bay, with a curved carapace length of 75 centimeters and width of 64 centimeters, he was recaptured on 22 June 2025 near the Las Garcitas Islets after becoming entangled in an artisanal longline. By then only one of his original tags remained, but tag V001M was enough to confirm his identity; he received two new tags and was released in good condition, his measurements essentially unchanged and his elongated tail again confirming his status as an adult male. Crucially, the recapture date fell at the peak of the nesting season, and the research team had also repeatedly observed solitary hawksbills and small groups of up to four individuals surfacing and engaging in courtship and mating near the Las Garcitas Islets during their surveys. Together, these observations provide the first preliminary evidence that adult male hawksbills occur in the Los Garzos Bay–Las Garcitas area during the breeding period, close to the rookery they would presumably serve.

The authors are careful, however, about what this record does and does not prove. A single recapture, however evocative, cannot demonstrate continuous residency, seasonal site fidelity, remigration periodicity, local male abundance, or reproductive connectivity between the males and the nesting females of the rookery. The fishery-dependent reports are opportunistic and subject to unknown reporting bias, so they document interactions rather than distribution. Two competing hypotheses now frame the next phase of work: either some adult males return repeatedly to the area across successive breeding seasons, or they appear only in breeding years separated by one or more skipped seasons, which would also produce a multi-year gap between sightings. Both possibilities echo questions better studied in male green and loggerhead turtles, whose breeding periodicity and breeding-area fidelity have been examined in places like the southern Great Barrier Reef. Environmental context may matter too: the Gulf of Paria’s anticyclonic circulation could help retain turtles locally, while seasonal productivity peaks during the June-to-November rainy season may shape the availability of the sponges and other benthic prey that hawksbills favor. A separate, remarkable record adds regional texture: a hawksbill originally tagged in Puerto Rico was recovered in Los Garzos Bay some 1,200 kilometers away, showing that at least some turtles using the gulf participate in much broader regional movements.

Turning to the future, the team argues that these findings justify neither immediate fishery closures nor the formal designation of the area as confirmed male habitat. Instead, they position the Las Garcitas Islets–Los Garzos Bay zone as a candidate site for targeted monitoring and participatory risk assessment with local fishers. Because the focal male was recaptured in fishing gear, the priority actions are practical: strengthening fisher reporting networks, promoting safe handling and release protocols, training crews, systematically documenting gear interactions, and encouraging photographic records of every capture. The researchers also lay out the technical toolkit needed to move from anecdote to evidence: satellite telemetry to trace male movements and residence times, multi-season mark–recapture programs to estimate abundance and fidelity, photo-identification to track individuals non-invasively, and genetic analyses to test whether the males near Las Garcitas actually fertilize clutches on the adjacent nesting beaches. Funding from the New England Aquarium’s Marine Conservation Action Fund, the International Sea Turtle Society, and Conservation Connect supported the work, and the collaboration of Macuro’s fishing communities proved indispensable at every step.

For now, one turtle’s two-year journey of barely two kilometers stands as a small, hard-won data point in a vast gap of knowledge. But its implications ripple outward. If male hawksbills gather near rookeries during breeding seasons, then the waters adjacent to nesting beaches, precisely the zones where artisanal fisheries operate, may be critical habitat that current conservation frameworks, built almost entirely around beaches and nesting females, simply do not see. Every additional recapture, every validated fisher report, and every satellite track from the Gulf of Paria will help determine whether the Gulf’s males are loyal residents of these shallow waters or intermittent visitors from distant foraging grounds, and whether protecting them requires seasonal measures negotiated with the very fishers whose nets and lines keep bringing these ghostly males back into view.

Subject of Research: First local flipper-tag recapture of an adult male hawksbill turtle near the Gulf of Paria rookery in Venezuela

Article Title: First local flipper-tag recapture of a male hawksbill turtle near a major rookery in the Gulf of Paria, Venezuela

Article References: Balladares, C., Garcia-Cruz, M., Alio, J., & Barrios-Garrido, H. (2026). First local flipper-tag recapture of a male hawksbill turtle near a major rookery in the Gulf of Paria, Venezuela. Frontiers in Amphibian and Reptile Science, 4, Article 1818436. https://doi.org/10.3389/famrs.2026.1818436

Image Credits: AI Generated

DOI: 10.3389/famrs.2026.1818436

Keywords: hawksbill turtle, sea turtles, male sea turtle ecology, mark-recapture, Gulf of Paria, Venezuela, operational sex ratio, artisanal fisheries, bycatch, rookery, Caribbean, conservation

The research, published in the journal Discover Oceans, surveyed 113 randomly selected artisanal fishermen at three landing centers, Ruela, Chibuabuare and Chuiba, between September and November 2024. The team, led by Heráclito Comia of Lúrio University, used semi-structured questionnaires administered face to face in Portuguese and the local language Emakua, a necessity in a population where more than half of respondents had no formal schooling. The sample was drawn from 146 registered fishermen using systematic sampling with a random starting point, and the data were analyzed with descriptive statistics and chi-square tests. The survey deliberately anchored questions to the previous five years, a window that cognitive psychology research suggests minimizes recall bias while capturing meaningful trends, and one that includes the traumatic memory of Cyclones Idai and Kenneth in 2019.

The numbers tell a story of partial awareness. Just under 62 percent of respondents said they had heard of climate change, a figure well below the near-universal awareness reported among fishers in Ghana and Nigeria. But awareness of the label tells only part of the story. When asked about specific environmental changes, the fishermen’s empirical observations were strikingly sharp: 91 percent perceived rising temperatures, 82 percent noted declining rainfall, 86 percent perceived rising sea levels, and a remarkable 98 percent reported more frequent cyclones. One 52-year-old fisherman from Ruela described the shift in visceral terms, saying the sun is much hotter now than when he started fishing, and that by ten in the morning the heat burns their skin where once they could stay out until midday.

Attribution is where the scientific and traditional worlds diverge most sharply. Nearly three quarters of respondents, 72.6 percent, attributed the changes to supernatural or divine forces rather than human activity, and only 27.4 percent acknowledged potential human contributions. One 65-year-old fisherman from Chuiba explained that the changes in the sea and the winds are controlled by the spirits of the ancestors, and that when ceremonies are not performed correctly or the sea is angered, the weather turns against the community. The researchers argue this attribution pattern matters enormously for policy, because belief in human agency is often a precondition for proactive adaptation. If the weather is a moral response to human behavior, the logic of emissions reduction or coastal planning simply does not compute.

The statistical analysis added nuance to the picture. Education level was strongly associated with climate change awareness, with those holding primary education or higher significantly more likely to recognize the term than those with no formal schooling, a moderate effect size confirmed by chi-square testing. Years of fishing experience, meanwhile, predicted the adoption of adaptation strategies: fishers with more than two decades on the water were far more likely to deploy multiple responses, suggesting that accumulated local ecological knowledge is itself a form of adaptive capacity. Intriguingly, perception of warming did not vary by age group, indicating that the experience of a hotter coast is shared across generations, and awareness did not differ significantly between landing centers.

What the fishermen are actually doing in response to change is arguably the most encouraging part of the study. The most common strategy, adopted by 36 percent, was abandoning mosquito nets, a cheap but destructive fishing method, in favor of proper drift nets, a shift the fishers describe as both a reaction to declining catches and a conscious conservation choice. One 38-year-old from Chibuabuare explained that mosquito nets were cheap but the fish were disappearing, and that drift nets cost more but catch bigger fish while the small ones can grow. A quarter of respondents reported avoiding juvenile fish, and a fifth said they deliberately avoided expanding their fishing zones. One elder put the logic plainly: if you catch the babies today, there will be no food for the children tomorrow.

But the study also exposes the hard ceiling that poverty places on adaptation. Poverty was named as the primary barrier by 41.6 percent of respondents, followed by lack of access to financial resources at 20.4 percent. The dilemma is captured by a 29-year-old fisherman from Chuiba who said he knows he should buy a motor to reach deeper, cooler water, but struggles just to buy food for his family and cannot imagine saving for an engine. Other constraints included restricted access to fishing grounds during conservation closures, lack of appropriate gear, limited access to government services, and competition from foreign fishing vessels. In the IPCC’s vulnerability framework of exposure, sensitivity and adaptive capacity, the fishers of Pemba score high on the first two and dismally on the third.

The information landscape shaping these perceptions is equally revealing. Radio was the dominant source of climate information, cited by 41.6 percent of respondents, followed by fisher-to-fisher communication at 28.3 percent. Formal channels, NGOs, researchers and extension services, barely registered, each mentioned by fewer than one percent of respondents. That near-total absence of institutional contact represents a critical failure of the science-society interface, the authors argue, and simultaneously points to a solution: radio broadcasts in Emakua and Portuguese, paired with peer-to-peer education networks, could carry scientific climate information into communities through channels they already trust. The researchers also propose engaging fishers as citizen scientists to record environmental changes, co-producing knowledge that is both scientifically valid and locally credible.

The wider stakes are considerable. Mozambique’s coastal and marine environment supports roughly two million people who depend directly on fisheries, and the artisanal sub-sector accounts for about 80 percent of total marine catches. Climate projections suggest temperatures in the country could rise by 1.5 to 2.5 degrees Celsius by 2100, and the 2019 cyclone season, which killed more than 600 people and displaced millions, offered a brutal preview of what intensifying extremes mean for coastal communities. The Pemba study’s recommendations therefore extend beyond climate communication to structural change: alternative livelihood programs such as sustainable aquaculture and ecotourism, subsidies for sustainable fishing gear, microfinance access, SMS and radio early-warning systems, community climate information centers at landing sites, and social protection measures such as cash transfers during closed seasons or weather-indexed insurance.

What emerges from Pemba is a lesson that resonates far beyond northern Mozambique. Local communities living on the front lines of climate change often perceive its fingerprints with precision, sometimes more vividly than distant institutions, but perception alone does not produce effective adaptation when explanations are supernatural, information is informal and money is scarce. The researchers call for longitudinal studies tracking how perceptions evolve, comparative work across Mozambique’s coastlines, and gender-disaggregated analyses, since women dominate fish processing and marketing yet were largely absent from this survey of registered fishers. Until the structural constraints of poverty and the cultural framing of climate causation are addressed together, the fishermen of Pemba will keep reading the sea accurately, and keep waiting for the spirits to calm it.

Subject of Research: Climate change perceptions and adaptation among artisanal fishing communities in northern Mozambique

Article Title: Artisan fishers’ perception of climate change: a case study of Pemba district, Northern Mozambique

Article References: Comia, H., Achia, S., & Machaieie, S. (2026). Artisan fishers’ perception of climate change: a case study of Pemba district, Northern Mozambique. Discover Oceans, 3(1), Article 9. https://doi.org/10.1007/s44289-026-00123-7

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00123-7

Keywords: climate change perception, artisanal fisheries, Mozambique, Pemba, adaptation strategies, coastal communities, local ecological knowledge, climate communication, vulnerability, Indian Ocean cyclones, fisheries conservation, adaptive capacity

The scale of the human stakes is enormous. India is the world’s second-largest fish producer, with a record 175.45 lakh tonnes of fish production in 2023, and its fisheries sector has grown by 10.87 percent since 2014–15. Odisha alone produces roughly 8.73 lakh metric tonnes annually, drawing on a 480 kilometre coastline and nearly 11 lakh hectares of inland and brackish waters. Globally, small-scale fisheries account for more than 90 percent of active fishers and support nearly two-thirds of the global fish catch, yet they remain chronically underreported in statistics and overlooked in policy. Chilika exemplifies this blind spot: more than 400,000 fishers live in nearly 150 settlements around the lagoon, many operating under a unique governance system that grants exclusive fishing rights administered through cooperatives and supported by the Chilika Development Authority.

Salinity in Chilika is governed by a delicate tug-of-war between seawater pushing in through tidal inlets from the Bay of Bengal and freshwater discharging from inland rivers. The lagoon spans nearly 1,100 square kilometres during the monsoon and contracts to about 906 square kilometres in the dry months, with an average depth of just 1.8 metres. This shallow, hydrologically dynamic system is divided into four ecological sectors: the freshwater-dominated Northern Sector, the Central and Southern Sectors, and the saline-rich Outer Channel. Seasonal salinity ranges from nearly zero during the rains to around 17 parts per thousand in winter and roughly 35 parts per thousand in summer, creating one of the steepest estuarine gradients in Asia and a natural laboratory for studying how salt shapes biodiversity.

The historical record reveals dramatic swings. Average salinity fell from 22.3 parts per thousand in 1957–1958 to between 9.4 and 11.8 parts per thousand by the early 1960s, and dropped to a critical low of 8.3 parts per thousand by 1999. The culprit was partly geomorphological: the commissioning of the Hirakud Dam on the Mahanadi River in 1957 unexpectedly increased the silt load entering the lagoon, driving progressive sedimentation, choking of the Arakhakuda mouth, reduced tidal exchange, salinity decline, and rampant weed overgrowth. In response, an artificial sea mouth was opened near Sipakuda village on 23 September 2000, restoring seawater ingress. Natural inlets subsequently formed at Gabakunda in 2008, Dhalabali in 2012, and during Cyclone Phailin in October 2013, and research by Panda and Mohanty showed that the shift from a single to a multiple inlet system between 2006 and 2009 produced pronounced changes in annual mean salinity, with cascading effects on sedimentation, marine species intrusion, and ecological balance.

Extreme weather adds another layer of volatility. The Super Cyclone of 1999 devastated fisheries resources and infrastructure. Cyclone Phailin in 2013 triggered a dramatic post-monsoon salinity decline and altered nutrient concentrations, lowering phosphate and nitrate while raising silicate and ammonia. Cyclone Fani in 2019, striking in May during the lagoon’s peak salinity period, instead elevated salinity relative to other storms, while Hudhud in 2014 had minimal impact. Data from 1999 to 2021 show average salinity of 10.69 parts per thousand, ranging from 0.1 to 36.9, with the Northern Sector experiencing sharp fluctuations and the Southern Sector remaining more stable. Most recently, a deep depression over the northwestern Bay of Bengal on 13 July 2022 opened a new inlet, driving Outer Channel salinity from 21 to 34 parts per thousand in June down to zero to 2 parts per thousand by August. Broader climate phenomena, including the El Niño–Southern Oscillation, modulate these patterns by influencing precipitation, river discharge, and lagoon–sea exchange.

The biological consequences are striking. Fish diversity in Chilika is structured along the salinity gradient: freshwater species dominate the north, brackish species the centre and south, and the tidal Outer Channel supports both brackish and marine fishes. Species counts have climbed from 138 aquatic species recorded in 1918 to 336 by 2008, including 261 finfish, 28 prawns, and 34 crabs, before slipping slightly to 317 in 2023 across 207 genera, 88 families, and 23 orders. The lagoon also shelters around 700 plant and 800 animal species, including the endangered Irrawaddy dolphin, and serves as a critical stopover on the Central Asian Flyway for migratory birds. Salinity shifts impose oxidative stress on aquatic organisms, altering survival, reproduction, and distribution, and declining salinity has stressed brackish biota such as prawns, which form the backbone of the local fishery.

The 2000 hydrological intervention, however, demonstrates that salinity management can also drive recovery. Enhanced seawater exchange improved recruitment of juvenile marine fish, lifting fish landings from 11,989 metric tonnes in 2001–02 to 14,228 metric tonnes in 2011–12, documenting 56 new species, and coinciding with the reappearance of the Irrawaddy dolphin. Phytoplankton communities responded too: diatoms replaced cyanobacteria and came to dominate up to 72 percent of phytoplankton biomass, benefiting fish production. After the new inlet opened in July 2022, landings rose to 223.62 metric tonnes, with mullets and other marine species featuring prominently. Yet fishers also reported disturbances, including sand infestation, fluctuating water depths, and the arrival of unfamiliar marine organisms such as stingrays, octopuses, and jellyfish, which reshaped fishing seasons and species composition.

Habitat degradation compounds the problem. Declining salinity converts brackish habitats into freshwater-dominated systems, eliminating niches for estuarine species such as mullets and anchovies, narrowing tidal channels, and degrading seagrass meadows that serve as critical spawning and feeding grounds for prawns and crabs. Long-term desalination has fuelled invasive weed growth, particularly in the northern sector, while excessive sedimentation and intensive prawn aquaculture, locally known as gheri or bund fishing, have altered hydrology and sediment transport, impeding fish migration and nutrient flow. Embankments and dams further disrupt natural flow, fragmenting habitats and reducing species resilience. The socioeconomic fallout is cascading: declining catches and unstable incomes exacerbate poverty, malnutrition, and occupational migration, and in some cases entire villages have shifted away from fishing altogether, while shrimp aquaculture introduced in the 1980s disrupted traditional access rights and intensified competition.

The review’s authors frame salinity not merely as a physical parameter but as a socio-ecological determinant linking ecological balance with human well-being, and they chart a path forward. Key strategies include restoring ecological buffers such as mangroves, seagrass beds, and wetlands that stabilize salinity and provide fish nurseries; promoting livelihood diversification through eco-tourism, aquaculture, and small enterprises; enforcing fisheries laws such as the Marine Fishing Regulation Acts in collaboration with local communities; and building fisher capacity in adaptive practices like seasonal restrictions, spatial management, and catch diversification. Regular monitoring of salinity and hydrological parameters is deemed indispensable for guiding adaptive management, and economic valuation shows fishery resources account for over 71 percent of the lagoon’s total economic value, underscoring what is at stake.

Ultimately, the study lays the groundwork for future econometric analyses quantifying how salinity variation cascades through biodiversity and artisanal livelihoods. As climate change accelerates sea-level rise, saltwater intrusion, and cyclone intensity across low-lying Asian coasts, Chilika’s experience offers a cautionary tale and a template: salinity management, if pursued inclusively and grounded in fishers’ rights, can allow Asia’s largest brackish water lagoon to thrive both as an ecological jewel and as a lifeline for the communities whose fortunes rise and fall with its salt.

Subject of Research: Salinity dynamics and their ecological and socioeconomic impacts on artisanal fisheries in Chilika Lagoon, India

Article Title: Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon

Article References: Nandy, A., Rout, D. S., & Tripathy, P. (2026). Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon. Discover Oceans, 3(1), Article 24. https://doi.org/10.1007/s44289-026-00137-1

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00137-1

Keywords: Chilika Lagoon, salinity, artisanal fisheries, brackish water, climate change, biodiversity, tidal inlets, cyclones, Odisha, small-scale fisheries, habitat degradation, hydrology