Littoral Research Articles

The distribution of macroalgae in the Aceh north-western coastline

Abstract Macroalgae are polyphyletic multicellular plants that generally inhabit the littoral zone of the seashore. Aceh Province has a coastline stretching along the east, north and west ends of Sumatra Island; thus, various macroalga species may be found. This research aims to study the distribution of macroalga species at four locations on the north-western side of Aceh, including three sites in Aceh Besar District (Lhoknga, Lange, and Ujung Pancu Beaches) and one site in Banda Aceh City (Ulee Lheue Beach). Sampling was done across 50 meters of the seashore and 1 meter towards the sea. The sampling was conducted using a 1×1 meter quadrant transect method with sampling points every 10 meters. The morphology determination shows that five species of macroalga grew at Lhoknga Beach, namely Valoniopsis pachynema, Halimeda opuntia, Turbinaria decurrens, Sargassum plagiophyllum, and Padina australis. Lange Beach had three macroalgae species: Chaetomorpha linum, Laurencia obtusa, and Sargassum plagiophyllum. Meanwhile, Ujung Pancu Beach has four macroalga species: Halymenia durvillei, Turbinaria decurrens, Ulva lactuca and Sargassum plagiophyllum. At Ulee Lheue Beach, five species were found: Gracilaria edulis, Caulerpa taxifolia, Hypnea musciformis, Padina australis, and Acanthophora spicifera. In total, 13 macroalga species were distributed on Aceh’s north-western coast.

Modern outlook on the source of the 551 AD tsunamigenic earthquake that struck the Phoenician (Lebanon) coast

On July 9th, 551 AD, a strong earthquake followed by a noticeable tsunami and another destructive shock hit the littoral zone of Phoenicia, currently Lebanon. The sequence of events was associated with active faults in the region, but the source able to explain both seismic and tsunami effects is still a matter of open debate. This article contributes to unlocking this enigma by providing a modern analysis of the historical accounts of macroseismic effects, earthquake environmental and tsunami effects, and archaeoseismic findings. Here, we conduct seismotectonic research, evaluate the intensities of all the associated effects, and perform coseismic deformation and numerical tsunami modeling to infer the most likely source. Our results suggest that either the thrust system noted as Mount Lebanon Thrust underlying Lebanon and crops out at the seabed offshore of the coast or the intermittent transpressive Tripoli-Batroun-Jounieh-Damour fault zone along the Lebanese coast are the best candidate sources for the 551 AD earthquakes and tsunami. Both of these sources allow us to better explain the macroseismic, morphological and tsunamigenic effects. Remarkably, the notable uplift of the coastal, marine-cut terraces along the Lebanese littoral zone is well reproduced by the coseismic uplift associated with these sources, thus also clarifying the considerable drawback of the sea and limited inundation reported by the historical accounts.

Vertical transfer of microplastics in nearshore water by cultured filter-feeding oysters

Microplastics (MPs) are widely distributed in the sea, but the vertical transfer of MPs by marine organisms in coastal area is still poorly understood. In this study, we used laser direct infrared (LDIR) spectroscopy to determine the number and characteristics of MPs deposited by cultured oyster Crassostrea gigas and further compared the differences between MPs of natural deposit and biodeposit in field environments. The amounts of MPs found in the biodeposit of cultured oysters were 3.54 times greater than that in the natural deposition. The polymer types of biodeposit MPs also differed from those of natural deposition. It was estimated that a single oyster can deposit 15.88 MPs per day, which is a figure much higher than the initial results, and hotspots of MPs deposition may be formed within the oyster aquaculture area. We used generalized linear mixed model (GLMM) to further infer the sources of MPs in sediments and found that distance to shore, cultured zone and urban center were important predictors of MPs abundance in sediments of aquaculture area. The above results suggest that cultured bivalves have an important capacity for MPs biodeposition and will further change the vertical distribution pattern of MPs in coastal environments.

Microplastic pollution in the Thumbprint emperor (Lethrinus harak) from Tanzanian coastal waters: Occurrence, abundance, characterization, and relevance as a monitoring species

In the present study we collected the Thumbprint emperor (Lethrinus harak) from seven landing sites from the coastal waters around Dar es Salaam and Zanzibar (Tanzania) to (i) quantify and characterize microplastics (MPs) in their digestive tracts and (ii) use previously assessed environmental levels in nearshore surface waters and seabed sediments to determine whether L. harak could be a relevant biomonitor for MP pollution in the region. L. harak (n=387) had an overall frequency of occurrence (FO%) of 48 % and displayed spatial variation between sites with Kunduchi (FO=66.7 %) and Mijimwena (FO=17.1 %) having the highest and lowest FO%, respectively. Fish from Mjimwema had a mean MP content of 0.17 ± 0.38 MPs individual-1 whilst fish from Kizimkazi had the highest MP abundance (1.75 ± 2.33 MPs individual-1). Fibers (overall 64.7 %, range across sites 48–86 %) and fragments (17.9 %, 5–25 %) were the most dominant MP types whilst black (46.9 %, 40–58 %) and blue (22.5%, 7–36 %) MPs were the most common colours. Fish length (ρ= -0.09, p=0.09) or weight (ρ=0.07, p=0.18) did not significantly correlate to MP abundance in fish (Spearman rank correlations). Neither MP occurrence nor abundance was linked to MP concentrations in either surface waters or seabed sediments (Spearman rank correlation), but MPs in the fish better reflected MPs in the sediment compared to surface water (two-way ANOVA on ranked data). Whilst L. harak presents as a promising candidate to monitor MP pollution along the East African coast due to its ecology, overall, it lacks reliability. Nonetheless, the present study fills important knowledge gaps both geographically on the East African Coast and with an underrepresented taxonomic family (Lethrinidae ‘Emporer fishes’).

On finding of an abundant population of free-living stages of ergasilids (Copepoda, Cyclopoida) in the Lyutoga river of Southern Sakhalin

In the littoral zone of the oxbow of the Lyutoga River (Southern Sakhalin), which remains connected to the main channel, a high population density of parasitic copepods was found (103 ind./m2). Ergasilus briani Markewitsch, 1933, widely distributed in Eurasia, but not previously recorded in South Sakhalin and noted only for one water body in northwestern Sakhalin (Lake Sladkoe), demonstrated the highest population density (98 ind./m2). The abundance of the second species, Thersitina gasterostei (Pagenstecher, 1861) was significantly lower (5 ind./m2). T. gasterostei has previously been noted in South Sakhalin, but the present finding is the first for the Lyutoga River. The high abundance of free-living stages of ergasilids is presumably related to the reproductive peak and the hydrological nature of the collection site (littoral area with a slow current and strong overgrowing with macrophytes).

Leeches Baicalobdella torquata feed on hemolymph but have a low effect on the cellular immune response of amphipod Eulimnogammarus verrucosus from Lake Baikal.

Lake Baikal is one of the largest and oldest freshwater reservoirs on the planet with a huge endemic diversity of amphipods (Amphipoda, Crustacea). These crustaceans have various symbiotic relationships, including the rarely described phenomenon of leech parasitism on amphipods. It is known that leeches feeding on hemolymph of crustacean hosts can influence their physiology, especially under stressful conditions. Here we show that leeches Baicalobdella torquata (Grube, 1871) found on gills of Eulimnogammarus verrucosus (Gerstfeldt, 1858), one of the most abundant amphipods in the Baikal littoral zone, indeed feed on the hemolymph of their host. However, the leech infection had no effect on immune parameters such as hemocyte concentration or phenoloxidase activity and also did not affect glycogen content. The intensity of hemocyte reaction to foreign bodies in a primary culture was identical between leech-free and leech-infected animals. Artificial infection with leeches also had only a subtle effect on the course of a model microbial infection in terms of hemocyte concentration and composition. Despite we cannot fully exclude deleterious effects of the parasites, our study indicates a low influence of a few leeches on E. verrucosus and shows that leech-infected amphipods can be used at least for some types of ecophysiological experiments.

Matching field-based ranges in brackish water gradients with experimentally derived salinity tolerances of Conrad’s false mussel (Mytilopsis leucophaeata cochleata) and zebra mussel (Dreissena polymorpha)

The invasive alien false mussels Mytilopsis leucophaeata cochleata and Dreissena polymorpha (Dreissenidae) have established populations in the North Sea canal in the Netherlands that connects the harbours of Amsterdam with the North Sea. The favourable and unfavourable salinity ranges of both species were earlier studied in long-term outdoor mesocosm experiments. Their occurrence in salinity gradients in estuaries or canals connecting seaways to freshwater harbours provides information on their salinity tolerance under field conditions. By the combination of laboratory experiments and field data using the same source population a high predictability can be expected for establishment of the gradients facilitated by constructions. The reliability of experimentally derived salinity-tolerance limits for both dreissenid species was tested using data on their distribution in a salinity gradient of the littoral zone along the North Sea canal. The mussels used for the survival experiments in mesocosms were also collected from this canal. Favourable salinity ranges for adult survival in the mesocosms were 0.2 – 17.5 for M. leucophaeata cochleata and 0.2 – 6.0 for D. polymorpha. Unfavourable salinities were outside these ranges and led to high and fast mortality of these species. Mytilopsis leucophaeata cochleata was present over nearly the whole length of the North Sea canal with the highest densities close to the sea sluices where also the highest salinities and water temperatures were measured. Their densities in the canal decreased gradually at larger distances from the sea. Dreissena polymorpha co-exists with M. leucophaeata cochleata at the east end of the canal with low salinity due to the influence of freshwater of the river Rhine. The occurrence of D. polymorpha was restricted to a salinity below 4 and M. leucophaeata cochleata only occurred at a salinity above 1.5 (maximum value measured in the canal 9.2). Shorter salinity gradients with lower salinity ranges provided additional information on the co-existence of both species. Co-existence was observed at a salinity range of 1.5–3.3 (own data), 1.0–3.5 (Van Couwelaar and Van Dijk 1989), both in the North Sea canal, and 0.2–2.8, in the Canal through Voorne (Janssen and Janssen-Kruit 1967). These data correspond with studies of both species by Walton (1996) in the Hudson River (salinity range 0–3). Found salinity ranges in the North Sea canal for both species match with the tolerance results obtained by mesocosm experiments. A new invading dreissenid mussel Dreissena rostriformis bugensis and a mytilid Ischadium recurvum occur in the North Sea canal since 2006 and 2012, respectively. Competition between recent and earlier invaders is likely when salinity tolerances are similar. It has already been observed that D. rostriformis bugensis outcompetes D. polymorpha under freshwater conditions (Bij de Vaate et al. 2014; Matthews et al. 2014). Ischadium recurvum has the potential to colonize large parts of the canal and to be a strong competitor of M. leucophaeata cochleata (Goud et al. 2019). Since January 2022, the new ‘Zeesluis IJmuiden’ with the biggest locks in the world is in use, affecting the probability of population establishment of new introduced and invasive alien mussel species.

Tracking Water Quality and Macrophyte Changes in Lake Trasimeno (Italy) from Spaceborne Hyperspectral Imagery

This work aims to show the potential of imaging spectroscopy in assessing water quality and aquatic vegetation in Lake Trasimeno, Italy. Hyperspectral reflectance data from the PRISMA, DESIS and EnMAP missions (2019–2022, summer periods) were compared with in situ measurements from WISPStation and used as inputs for water quality product generation algorithms. The bio-optical model BOMBER was run to simultaneously retrieve water quality parameters (Chlorophyll-a (Chl-a) and Total Suspended Matter, (TSM)) and the coverage of submerged and emergent macrophytes (SM, EM); value-added products, such as Phycocyanin concentration maps, were generated through a machine learning approach. The results showed radiometric agreement between satellite and in situ data, with R2 > 0.9, a Spectral Angle < 10° and water quality mapping errors < 30%. Both SM and EM coverage varied significantly from 2019 (135 ha, 0 ha, respectively) to 2022 (2672 ha, 343 ha), likely influenced by changes in rainfall and lake levels. The areas of greatest variability in Chl-a and TSM were identified in the littoral zones in the western side of the lake, while the highest variation in the fractional cover of SM and density of EM were observed in the south-eastern region; this information could support the water authorities’ monitoring activities. To this end, further developments to improve the reference field data for the validation of water quality products are recommended.

Response of Shallow-Water Temperature and Significant Wave Height to Sequential Tropical Cyclones in the Northeast Beibu Gulf

Using shallow-water buoy observations, reanalysis data, and numerical models, this study analyzes the variations in sea temperature and significant wave height (SWH) caused by two sequential tropical cyclones (TCs) ‘Lionrock’ and ‘Kompasu’ in October 2021 in the northeast Beibu Gulf, South China Sea. The results show that the sea surface temperature (SST) cooling of the nearshore waters was larger than the offshore water in the basin of the gulf, with the cooling amplitude and rate decreasing and the cooling time lagging behind wind increasing from coast to offshore. The near-surface temperature at the buoy station had a maximum decrease of 2.8 °C after ‘Lionrock’, and the decrease increased slightly to 3 °C after the stronger wind of ‘Kompasu’. The total decrease of 4.6 °C indicates that the sequential TCs had a superimposed effect on the cooling of the Beibu Gulf. The heat budget analysis revealed that the sea surface heat loss and the Ekman pumping rate in the nearshore waters during ‘Kompasu’ (−535 W/m2 and 5.8 × 10−4 m/s, respectively) were significantly higher than that (−418 W/m2 and 4 × 10−4 m/s) during ‘Lionrock’. On the other hand, the SST cooling (−1.2 °C) during the second TC is smaller than (−1.6 °C) the first weaker TC in the gulf basin, probably due to the deepening of the mixed layer. During the observation period, the waves in the Beibu Gulf were predominantly wind-driven. The maximum SWHs reached 1.58 m and 2.3 m at the bouy station near shore during the two TCs, and the SWH variation was highly correlated to the wind variation with a correlation of 0.95. The SWH increases from the nearshore to offshore waters during the TCs. The SAWN and ARCIRC coupled model results suggest that wave variations in the Beibu Gulf are primarily influenced by water depth, bottom friction, and whitecapping. Two days after the TCs, sea surface cooling and high waves appeared again due to a cold air event.

Exploring Wave-Vegetation Interaction At Blade Scale: A Comprehensive Analysis Of A Flexible Cylinder Through Experimental Data And A Direct Numerical Simulation

Aquatic vegetation in the littoral zone, particularly seagrass, is gaining increasing recognition for its net positive impact on the hosting environment. This recognition is rooted in its capacity to absorb wave energy, regulate water flow, and manage nutrient levels, sedimentation and accretion. Thus, there is a growing interest in integrating seagrass as a key component of a comprehensive climate-conscious strategy (Ondiviela et al., 2014). An effective approach to quantify the positive potential of seagrasses in altering coastal wave dynamics is by using numerical models. These numerical models operate at various spatio- temporal scales, ranging from large domains and multiple years to just a few regular waves in high resolution CFD numerical simulations. Zeller et al. (2014) classified these models, operating at different scales into three categories, each addressing the wave-vegetation interaction at a distinct scale: (1) blade scale, (2) meadow scale, and (3) ecosystem scale. The aim of the present study is to investigate the interaction between waves and vegetation at the blade scale. The primary objectives are two: first, to introduce a direct numerical technique that involves a two-way coupling between a fluid solver and a structural solver, and second, to present novel experimental data for a single flexible cylinder (Reis, 2022) serving as validation for the present (and future) numerical model(s).

Habitat segregation by sympatric juvenile Arctic charr and brown trout in shallow lake areas: a consequence of interspecific differences in predator avoidance?

In sympatry, juvenile brown trout (Salmo trutta) usually occupy the shallow and most productive areas (littoral zone) of lakes, while juveniles of Arctic charr (Salvelinus alpinus) are found in deeper, less productive parts. In contrast, when Arctic charr juveniles occur in allopatry, they often occupy shallow littoral areas as well. Habitat segregation has traditionally been interpreted as a trade-off between predation risk and energy gain, while the segregation of these two species has been explained by brown trout being more aggressive and competitively superior to Arctic charr. We hypothesize, however, that the marked habitat segregation between the two species may also be due to differences in predator avoidance. Accordingly, we conducted several laboratory tests, using Arctic charr and brown trout as potential predators. Live fish of the same species were offered as prey, either as small charr only, small trout only, or both small charr and small trout together. Artificial shelters were then introduced to examine the avoidance ability of prey fish against predatory fish. Our results showed that under these circumstances, access to shelters strongly decreased mortality in juvenile brown trout, but had no effect on juvenile Arctic charr mortality. Thus, the habitat segregation shown by sympatric juvenile Arctic charr and brown trout in lakes may be a consequence of interspecific differences in predator avoidance.

Observations of coastal infragravity wave characteristics under swell-dominated conditions

This study analyzed the characteristics of infragravity (hereafter IG) waves under a microtidal and swell-dominated wave climate based on the field observations collected in the nearshore waters (water depth: ∼ 13 m) of southern Sri Lanka. The main focus is on the dependence of nearshore IG waves on the incident short wave parameters, with particular attention to the influence of the short wave spectral shape on the IG wave characteristics. The observation results indicate that IG waves are primarily locally excited by incident swell wave energy, and accurate prediction of the IG wave height can be achieved using the parameter HS2Tm−1,0, which represents the short wave energy flux. Bound IG wave energy is much smaller than the free IG wave under conventional sea states but becomes significant under high-energy swell sea states.Higher levels of IG wave energy are found to be forced under narrower spectral shapes and smaller directional spreading short wave conditions, and these conditions typically correspond to stronger coupling strengths in the bound IG wave theory. Compared to the single-peaked spectra wave condition, the forced IG wave energy decreases under the double-peaked spectra wave condition. This is likely mainly because the latter tends to have a broader spectrum and a larger directional spreading. On the other hand, under the narrow-banded spectral short wave conditions, IG wave energy is inclined to be distributed over a lower and smaller frequency range. This is noteworthy because lower-frequency IG waves tend to be more difficult to break. In addition, the bound IG wave energy was found to increase at low tide, but for the intermediate water depths in which the observation site is located in this study, the influence of the small tidal range in the study area on the IG wave energy was not significant.

Making temporal dynamics relevant: The role of macrophytes in the phenological complexity of a shallow freshwater lake

AbstractA multidisciplinary approach demonstrates how submerged macrophytes generate high phenological variability in Hungary's Lake Balaton. A 239‐month time series of water chlorophyll indices derived from Landsat 7 imagery from 1999 to 2019 was used. These data facilitated the generation of area‐based phenological patterns, which allowed an assessment of phenological variability by correlating chlorophyll index sequences with spatially adjacent values. The results showed that phenological variability was consistently low (below 5%) at the farthest points from the shore, indicating uniform phenological processes in the pelagic zone of Lake Balaton. Conversely, the littoral zone showed almost eight times higher variability, indicating increased diversity in shallow water areas. In particular, extensive macrophyte biomass datasets revealed a direct relationship between increased phenological variability in the littoral zone and macrophyte biomass (Spearman rank correlation: 0.893). This research highlights contrasting phenological patterns between phytoplankton and macrophyte communities, driven by different life cycles, and the possibility of effectively using satellite data to delineate phenological separation within lakes.

Comparative Evaluation of Semi-Empirical Approaches to Retrieve Satellite-Derived Chlorophyll-a Concentrations from Nearshore and Offshore Waters of a Large Lake (Lake Ontario)

Chlorophyll-a concentration (Chl-a) is commonly used as a proxy for phytoplankton abundance in surface waters of large lakes. Mapping spatial and temporal Chl-a distributions derived from multispectral satellite data is therefore increasingly popular for monitoring trends in trophic state of these important ecosystems. We evaluated products of eleven atmospheric correction processors (LEDAPS, LaSRC, Sen2Cor, ACOLITE, ATCOR, C2RCC, DOS 1, FLAASH, iCOR, Polymer, and QUAC) and 27 reflectance indexes (including band-ratio, three-band, and four-band algorithms) recommended for Chl-a concentration retrieval. These were applied to the western basin of Lake Ontario by pairing 236 satellite scenes from Landsat 5, 7, 8, and Sentinel-2 acquired between 2000 and 2022 to 600 near-synchronous and co-located in situ-measured Chl-a concentrations. The in situ data were categorized based on location, seasonality, and Carlson’s Trophic State Index (TSI). Linear regression Chl-a models were calibrated for each processing scheme plus data category. The models were compared using a range of performance metrics. Categorization of data based on trophic state yielded improved outcomes. Furthermore, Sentinel-2 and Landsat 8 data provided the best results, while Landsat 5 and 7 underperformed. A total of 28 Chl-a models were developed across the different data categorization schemes, with RMSEs ranging from 1.1 to 14.1 μg/L. ACOLITE-corrected images paired with the blue-to-green band ratio emerged as the generally best performing scheme. However, model performance was dependent on the data filtration practices and varied between satellites.

Water Level Fluctuation Effect on Fish Reproduction Success

Alteration of water levels of the lake/reservoir due to changes in river discharges, upstream abstraction, and drawdown regulation due to hydropower generation has been reported as among the major challenges to fish physiology and ultimately reproduction. Variations in lake/reservoir water levels influence biodiversity and the abundance of lake/reservoir biota. Variations have the greatest impacts in the littoral zones hence, interfering with fish spawning, incubation, and hatching of eggs, as well as the development of larvae, postlarvae, and juveniles. This particular paper reviews the literature available on the effect of the reservoirs/lakes’ water level fluctuations on fish reproduction success using the documentary view method. The literature argues that water level fluctuations have both positive and negative impacts depending on frequency, magnitude, and duration and the species exposed. Extreme fluctuations tend to bring more adverse impacts. It further indicates that extreme and untimely water level fluctuation has direct impacts on the aquatic habitats and ultimately impacts fish assemblage and their populations. Few articles indicate the range of decrease or increase of water level, duration of such events, and effects they have on reservoir/lake ecosystem functions and fish physiology. Nevertheless, quantification of moderate and extreme water level fluctuation and associated effects is lacking. Although water level fluctuation is an important environmental cue for aquatic organisms, literature shows that the reduction of extreme water level variations especially multiannual variations is vital for fish reproduction. Therefore, upstream water use and reservoir operations should take into consideration the effects of water level fluctuations on reservoir structure, biological functions, and ultimate effects on fish reproduction.

Zooplankton community structure and diel migration patterns vary over hours, days, and years in the pelagic and littoral zone of a eutrophic reservoir

Abstract Zooplankton play an integral role as indicators of water quality in freshwater ecosystems, but exhibit substantial variability in their density and community composition over space and time. This variability in zooplankton community structure may be driven by multiple factors, including taxon-specific migration behavior in response to environmental conditions. Many studies have highlighted substantial variability in zooplankton communities across spatial and temporal scales, but the relative importance of space vs. time in structuring zooplankton community dynamics is less understood. In this study, we quantified spatial (a littoral vs. a pelagic site) and temporal (hours to years) variability in zooplankton community structure in a eutrophic reservoir in southwestern Virginia, USA. We found that zooplankton community structure was more variable among sampling dates over 3 years than among sites or hours of the day, which was associated with differences in water temperature, chlorophyll a, and nutrient concentrations. Additionally, we observed high variability in zooplankton migration behavior, though a slightly greater magnitude of DHM vs. DVM during each sampling date, likely due to changing environmental conditions. Ultimately, our work underscores the need to continually integrate spatial and temporal monitoring to understand patterns of zooplankton community structure and behavior in freshwater ecosystems.

Three decades of nearshore surveys reveal long-term patterns in gray whale habitat use, distribution, and abundance in the Northern California Current

The nearshore waters of the Northern California Current support an important seasonal foraging ground for Pacific Coast Feeding Group (PCFG) gray whales. We examine gray whale distribution, habitat use, and abundance over 31 years (1992–2022) using standardized nearshore (< 5 km from shore) surveys spanning a large swath of the PCFG foraging range. Specifically, we generated density surface models, which incorporate detection probability into generalized additive models to assess environmental correlates of gray whale distribution and predict abundance over time. We illustrate the importance of coastal upwelling dynamics, whereby increased upwelling only yields higher gray whale density if interspersed with relaxation events, likely because this combination optimizes influx and retention of nutrients to support recruitment and aggregation of gray whale prey. Several habitat features influence gray whale distribution, including substrate, shelf width, prominent capes, and river estuaries. However, the influence of these features differs between regions, revealing heterogeneity in habitat preferences throughout the PCFG foraging range. Predicted gray whale abundance fluctuated throughout our study period, but without clear directional trends, unlike previous abundance estimates based on mark-recapture models. This study highlights the value of long-term monitoring, shedding light on the impacts of variable environmental conditions on an iconic nearshore marine predator.

Coexistence, resource partitioning, and fisheries management: A tale of two mesopredators in equatorial waters.

Rock hind (Epinephelus adscensionis) and spotted moray (Gymnothorax moringa) are ubiquitous mesopredators that co-occur in the nearshore waters of Ascension Island in the South Atlantic Ocean, where they have significant cultural and subsistence value, but management of their non-commercial take is limited. This isolated volcanic system is home to high biomass and low species diversity, which poses two key questions: How can two mesopredators that perform similar ecological roles coexist? And if these two species are so ecologically similar, can they be managed using the same approach? Here, we combined acoustic telemetry, stomach content analysis, and stable isotope analysis to (i) explore space use and diet choices within and between these two species and (ii) to assess appropriate species-specific management options. Although rock hind had high residency and small calculated home ranges (0.0001-0.3114 km2), spotted moray exhibited shorter periods of residency (<3 months) before exiting the array. Vertical space use differed significantly across the 20-month tracking period, with individual differences in vertical space observed for both species. A hierarchical generalized additive model using 12-h averaged depth data identified that rock hind occurred lower in the water column than spotted moray, with both species occupying moderately deeper depths at night versus day (+1.6% relative depth). Spotted moray depth was also significantly predicted by lunar illumination. Aggregating samples by species and tissue type, Bayesian ecological niche modeling identified a 53.14%-54.15% and 78.02%-97.08% probability of niche overlap from fin clip and white muscle, respectively, whereas limited stomach content data indicated a preference for piscivorous prey. Variability in niche breadth between years suggests these species may exploit a range of prey items over time. These findings indicate that although these two species perform a similar ecological role by feeding on prey occupying the same trophic levels, subtle differences in movement behaviors between them suggest a one-rule-fits-all management approach is not likely the most effective option.

Construction of Aerosol Model and Atmospheric Correction in the Coastal Area of Shandong Peninsula

Applying standard aerosol models for atmospheric correction in nearshore coastal waters introduces significant uncertainties due to their inability to accurately represent aerosol characteristics in these regions. To improve the accuracy of remote sensing reflectance (Rrs) products in the nearshore waters of the Shandong Peninsula, this study develops an aerosol model based on aerosol data collected from the Mu Ping site in the coastal area of the Shandong Peninsula, enabling tailored atmospheric correction for this specific region. Given the pronounced seasonal variations in aerosol optical properties, monthly aerosol models were developed. The monthly aerosol model is derived using the average values of aerosol microphysical properties. Compared to the standard aerosol model, this model is more effective in characterizing the absorption and scattering characteristics of aerosols in the study area. Corresponding lookup tables for the aerosol model were created and integrated into the NIR-SWIR atmospheric correction algorithm. According to the accuracy evaluation indexes of RMSD, MAE, and UPD, it can be found that the atmospheric correction results of the aerosol model established in this paper are better than those of the standard aerosol model, especially in the 547 nm band. It demonstrates that the new aerosol model outperforms the standard model in atmospheric correction performance. With the increasing availability of aerosol observational data, the aerosol model is expected to become more accurate and applicable to other satellite missions.

Decomposition of exotic versus native aquatic plant litter in a lake littoral zone: Stoichiometry and life form analyses

The decomposition rates and stoichiometric characteristics of many aquatic plants remain unclear, and our understanding of material flow and nutrient cycles within freshwater ecosystems is limited. In this study, an in-situ experiment involving 23 aquatic plants (16 native and 7 exotic species) was carried out via the litter bag method for 63 days, during which time the mass loss and nutrient content (carbon (C), nitrogen (N), and phosphorus (P)) of plants were measured. Floating-leaved plants exhibited the highest decomposition rate (0.038 ± 0.002 day−1), followed by submerged plants and free-floating plants (0.029 ± 0.002 day−1), and emergent plants had the lowest decomposition rate (0.019 ± 0.001 day−1). Mass loss by aquatic plants correlated with stoichiometric characteristics; the decomposition rate increased with an increasing P content and with a decreasing C content, C:N ratio, and C:P ratio. Notably, the decomposition rate of submerged exotic plants (0.044 ± 0.002 day−1) significantly exceeded that of native plants (0.026 ± 0.004 day−1), while the decomposition rate of emergent exotic plants was 55 ± 4 % higher than that of native plants. The decomposition rates of floating-leaved and free-floating plants did not significantly differ between the native and exotic species. During decomposition, emergent plants displayed an increase in C content and a decrease in N content, contrary to patterns observed in other life forms. The P content decreased for submerged (128 ± 7 %), emergent (90 ± 5 %), floating-leaved (104 ± 6 %), and free-floating plants (32 ± 6 %). Exotic plants released more C and P but accumulated more N than did native plants. In conclusion, the decomposition of aquatic plants is closely linked to litter quality and influences nutrient cycling in freshwater ecosystems. Given these findings, the invasion of the littoral zone by submerged and emergent exotic plants deserves further attention.