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Lakes play an important role in the global carbon cycle, emitting significant amounts of the carbonic greenhouse gases, CO₂ and methane (CH₄). Nearly all lake studies have reported oxygenated surface waters oversaturated with (and thus continuously emitting) CH₄, yet no consistent explanation exists to account for why CH₄, which is produced in anoxic zones and consumed in the presence of oxygen, remains in oxic waters across the range of lake sizes. Here, we developed a physical model that defines the spatial CH₄ distribution in the surface waters of lakes as a function of CH₄ transport from the littoral zone including air–water gas exchange, and tested this in a set of 14 lakes that ranged widely in size (0.07–19,000 km²). Although the model adequately resolved the overall CH₄ decline within a lake relative to distance from shore across the range of lake sizes, discrepancies between observations and predictions suggest that other processes modulate surface CH₄ distributions. Coupled trends in the stable carbon isotopic signature of CH₄ further indicate that the spatial pattern in 30% of the lakes was dominated by a net loss via oxidation, whereas a net input of ¹³C-depleted CH₄ dominated the spatial pattern in 70% of the lakes, suggesting the predominance of pelagic CH₄ production in the oxic epilimnia of these lakes. The spatial patterns imposed by the interaction between physical and biological processes may result in a size-dependent underestimation of wholelake CH₄ emissions when based on center samples. Whereas the actual contributions of oxidation and eplimnetic CH₄ production are still not well understood, our results demonstrate that the ubiquitous CH₄ oversaturation observed in most lakes can be explained through the interaction between horizontal transport of littoral CH₄, air–water gas exchange and the balance between epilimnetic CH₄ oxidation and production.

Ebullitive methane (CH4) emissions in lentic ecosystems tend to concentrate at river‐lake interfaces and within shallow littoral zones. However, inconsistent definitions of the littoral zone and static representations of the lake or reservoir surface area contribute to major uncertainties in greenhouse gas (GHG) emissions estimates, particularly in reservoirs with large water‐level fluctuations. This study examines temporal variation in littoral and total surface areas of US reservoirs and demonstrates how different methods and data sources lead to discrepencies in reservoir GHG emissions at large scales and over time. We also explore variability in remotely sensed water occurrence according to maximum surface area, reservoir purposes, and hydrologic regions. Notably, the largest relative variability in surface area is exhibited by small reservoirs with a maximum surface area <1 km2 and non‐hydroelectric reservoirs. Additionally, we use a case study of measured CH4 emissions from the southeastern United States (Douglas Reservoir) to illustrate the effects of varying surface area on reservoir‐wide GHG estimates. Upscaled CH4 emissions in Douglas Reservoir differed by nearly two‐fold depending on the source of total surface area data and whether estimates accounted for seasonal fluctuations in surface area. During seasonal drawdown in Douglas Reservoir, relative littoral area varies non‐linearly; periods of lower pool elevation (and thus larger relative littoral area) likely contribute disproportionately high CH4 emission rates compared to the commonly sampled summer season when water levels are at full‐pool elevation. Improved GHG monitoring and upscaling techniques require accounting for temporal variability in reservoir surface extent and littoral area. Plain Language Summary Reservoirs can emit methane through several pathways, including bubbling from sediments which occurs most often in shallow zones. Different methods for estimating the area of this zone and disagreements in waterbody data sets results in uncertainty for large‐scale estimates of waterbody characteristics and methane emissions. Water detection algorithms applied to historical satellite imagery show that smaller reservoirs and those used for non‐hydroelectric purposes tend to have the highest variability in relative surface area. The high seasonal variability in both surface area and measured methane emissions, which contributes to uncertainty in the overall reservoir GHG footprint, is illustrated using data collected from Douglas Reservoir, in East Tennessee, USA. Key Points Estimates of total surface area and littoral area of US reservoirs vary three‐to four‐fold depending on the source of data and depth threshold used to delineate littoral area Relative to their maximum extent, the area of larger and hydroelectric reservoirs fluctuates less than small and nonhydroelectric reservoirs; interannual and seasonal recurrence of water is also more consistent in large reservoirs Estimates of reservoir GHG emissions based on field‐measured methane and carbon dioxide should account for fluctuations in lake levels and surface area

Bragath, R.C.; Sivakholundu, K.M., and Chandramohan, P., 2024. Nearshore sediment exchange process around the Cape Comorin, the peninsular tip of India. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 321-325. Charlotte (North Carolina), ISSN 0749-0208. Researchers have explored sediment transport's mechanism around the world's capes less than other coastal regions due to the multifaceted nearshore environment. Though recent research on nearshore sediment transport has advanced well, the complexity of sediment exchange around a Cape must be understood better. The coastal belt of Kanyakumari (Cape Comorin), India extends about 15 km on the east, bordering the Bay of Bengal, and about 55 km on the west, bordering the Arabian Sea with its confluence at the Indian Ocean. Unlike India's east and west coasts, the Kanyakumari coast follows a unique phenomenon in the coastal process, having peculiar wave climates resulting from the combined influences of ocean climate. The critical factor that causes changes in coastal configuration at the peninsular tip is the behavior of sediment transport. Most importantly, the exchange of sediments between the east and west coasts around this peninsular region is significant in determining the littoral drift pattern over the rest of the Indian coast. The present research work has studied the continuous movement of longshore currents over the peninsular tip using detailed active Littoral Environment Observation (LEO) for non-monsoon and monsoon seasons with varying wave climates and also relied on earlier studies taken up around the cape and assessed the significance of sediment transport around this littoral barrier. Field observations indicated that the littoral sediments reaching any potential barrier are likely to drift offshore and partly bypass to the adjacent cells within 20 m depth and partly deposited offshore during monsoon season. The sediments deposited offshore reach the beach again during fair weather, and such onshore movement builds up the stability of the eroded beach. During the ensuing monsoon period, these deposited sediments on the berm get eroded, carried into the sea, and deposited as offshore bars and maintain the beach's stability, providing enough sediment supply to the littoral cell system around the cape. The study highlights the significance of coastal dynamics and the interplay of nearshore sediment transport around the peninsular tip. We have also used mathematical modeling techniques to understand the hydrodynamic regime and the associated sediment exchange process.

Differences between peak-season and off-season dry mass, organic matter mass, and both concentrations and pools (standing stocks) of ash, N, P, K, Ca, Mg and Na were investigated in the rhizosphere soil, and live and dead aboveground plant biomass at 14 sites hosting 4 plant community types in the littoral zone of a eutrophic ancient shallow reservoir of about 5 km 2 area, the Rožmberk fishpond (S. Bohemia, CZ). Comparisons between the peak-season and off-season data and several stoichiometric relations calculated from them provided an insight into the mineral nutrient economy of the examined types of the fishpond littoral vegetation. It is rooted in relatively nutrient-poor sandy soil, but differently enriched with nutrients contained in either the percolating fishpond water, or that of springs located at the landward edge of the littoral zone. The degree of eutrophication of our sampling sites and their vegetation thus seem to be positively correlated with the degree of contact of the plants´ rhizosphere with the nutrient-richer fishpond or spring water.

Maddox, W.R., 2024. A case study of post-industrial shoreline recovery on Canada's Pacific Coast. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 305-309. Charlotte (North Carolina), ISSN 0749-0208. Intensive industrial activity led to rapid geomorphic change of the shoreline in Royal Roads Bay, on southern Vancouver Island, and the cessation of this activity resulted in reversion of the shore towards its pre-industrialized state. Littoral drift of byproduct from gravel mining and transport produced broad sand beaches along a previously cobbled shoreline, reducing erosion to steep supratidal slopes. Improved industrial practices depleted sediment supply and closure of the mine eventually ceased all anthropogenic input to the shoreline, inducing significant shoreline retreat. Volumetric quantification of seasonal sedimentation patterns was completed through repeat surveys encompassing storm season and periods of relatively low geomorphic change. Qualitative research was conducted to substantiate findings of overall sediment loss on the beach platform through the comparison of aerial photographs, satellite imagery, and in-situ photographs. Historical documents and archaeological evidence were incorporated to determine the pre-industrialized state of the shoreline. Results indicate that the dunes created by industrial byproduct prevented natural erosion of the supratidal cliffs leading to long term stability of the shoreline. In the post-industrial period, cliff toe erosion has become the primary source of mixed-clast sediment deposition. The brief modern period of industrial impact to this site permits a unique comparison between a known pre-industrialized and quantified post-industrialized state of an anthropogenically modified shoreline.

In this study, we quantify the differences in gross primary production (GPP), respiration (R), and algal nutrient limitation (nitrogen and phosphorus) in the littoral and pelagic habitats of an oligotrophic Patagonian lake (southern South America). We used submerged high frequency sensors that measure light, temperature, and dissolved oxygen and wind data to calculate GPP and R in both lake habitats. In addition, we carry out nutrient enrichment bioassays with nitrate, ammonium, and phosphate to determine which nutrient(s) limit algal growth in each lake habitat. On average, the productivity rate was 7.2 times higher at the epi-littoral (32.0 to 5.3 mmol O 2 m −2 d −1 ) relative to the epi-pelagic (4.1 to 1.3 mmol O 2 m −2 d −1 ). Algal growth in the littoral habitat was limited by nitrate and ammonium, while the pelagic habitat was co-limited by nitrogen (nitrate or ammonium) and phosphorus. Our work demonstrates that the littoral habitat of a Patagonian oligotrophic lake is more productive than the pelagic habitat and that the nutrients limiting algal growth in both habitats are different. These results underscore habitat variations and their significance in shaping the lake’s trophic dynamics for the first time in the southern hemisphere.

Some biological invasions can result in algae blooms in the nearshore of clear lakes. We studied if an invasive crayfish (Pacifastacus leniusculus) modified the biomass and community composition of benthic macroinvertebrates and therefore led to a trophic cascade resulting in increased periphyton biomass, elevated littoral primary productivity, and benthic algae bloom in a lake with remarkable transparency [Crater Lake, Oregon, USA]. After quantifying the changes in the spatial distribution of invasive crayfish over a 13-year period, we compared biomass and community composition of littoral–benthic macroinvertebrates, periphyton biovolume, community composition, nutrient limitation, and the development of benthic algae bloom in locations with high and low crayfish density. In addition, we determined if the alteration in community structure resulted in directional changes to gross primary production and ecosystem respiration. The extent of crayfish distribution along the shoreline of Crater Lake doubled over a 13-year period, leaving less than 20% of the shoreline free from crayfish. At high crayfish density sites, benthic macroinvertebrate biomass was 99% lower, and taxa richness was 50% lower than at low crayfish areas. High crayfish sites show tenfold greater periphyton biovolume, sixfold higher periphyton biomass (chlorophyll a), twofold higher metabolic productivity, and the presence of large filamentous algae (Cladophora sp.). The invasion of crayfish had negative consequences for a lake protected under the management of the USA National Park Service, with direct impacts on many levels of ecological organization.

Metabarcoding is by now a well‐established method for biodiversity assessment in terrestrial, freshwater, and marine environments. Metabarcoding data sets are usually used for α‐ and β‐diversity estimates, that is, interspecies (or inter‐MOTU [molecular operational taxonomic unit]) patterns. However, the use of hypervariable metabarcoding markers may provide an enormous amount of intraspecies (intra‐MOTU) information mostly untapped so far. The use of cytochrome oxidase (COI) amplicons is gaining momentum in metabarcoding studies targeting eukaryote richness. COI has been for a long time the marker of choice in population genetics and phylogeographic studies. Therefore, COI metabarcoding data sets may be used to study intraspecies patterns and phylogeographic features for hundreds of species simultaneously, opening a new field that we suggest to name metaphylogeography. The main challenge for the implementation of this approach is the separation of erroneous sequences from true intra‐MOTU variation. Here, we develop a cleaning protocol based on changes in entropy of the different codon positions of the COI sequence, together with co‐occurrence patterns of sequences. Using a data set of community DNA from several benthic littoral communities in the Mediterranean and Atlantic seas, we first tested by simulation on a subset of sequences a two‐step cleaning approach consisting of a denoising step followed by a minimal abundance filtering. The procedure was then applied to the whole data set. We obtained a total of 563 MOTUs that were usable for phylogeographic inference. We used semiquantitative rank data instead of read abundances to perform AMOVAs and haplotype networks. Genetic variability was mainly concentrated within samples, but with an important between seas component as well. There were intergroup differences in the amount of variability between and within communities in each sea. For two species, the results could be compared with traditional Sanger sequence data available for the same zones, giving similar patterns. Our study shows that metabarcoding data can be used to infer intra‐ and interpopulation genetic variability of many species at a time, providing a new method with great potential for basic biogeography, connectivity and dispersal studies, and for the more applied fields of conservation genetics, invasion genetics, and design of protected areas.

In the benthos of lakes, habitat size and structure as well as oxygen or resource availability can affect species distribution at local scales. By contrast, there is little knowledge about the mechanisms that determine the structure of benthic communities at larger scales. Here, we compiled data from the literature (23 studies monitoring 129 sites from 75 lakes located in central and northern Europe) to search for broad patterns in abundance, biomass, and community structure linked to lake trophic state (oligo-, meso-, or eutrophic), habitat features (hard vs. soft substrates), and water depth (littoral vs. profundal). The benthic meiofauna appeared much more abundant in the periphyton, and biomass was lower in oligotrophic lakes. Focusing on free-living nematodes, community structure differed markedly in hard vs soft substrates. Further, nematodes were especially dominant in profundal zones, where their diversity was significantly influenced by lake trophic state. In profundal zones of eutrophic lakes, nematode assemblages were less diverse and dominated by larger, mostly omnivorous or predacious taxa.

J. Vidinha, F. Rocha, C. and rade, C. Gomes and C. Freitas, 2007. Clay minerals – a mineralogical tool to distinguish beach from dune sediments. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 216 – 220. Gold Coast, Australia, ISSN 0749.0208 The usually textural parameters of sand sediments employed in order to distinguish present-day beach and dune deposits has been a matter of discussion in coastal studies. The results of these studies suggest that it may not be efficient to discriminate when the referred deposits exhibit well-sorted coastal sands, as was observed in limited coastal sections of the Portuguese coast. An innovative mineralogical approach based upon the study of the fine-grained fraction trapped in coastal sands, supported on univariate and multivariate statistical analysis, has been previously applied to a test area in the western Portuguese coast. This paper presents results from the mineralogical study of the clay fraction entrapped in coastal sand samples from the Espinho - Mondego Cape coastal sector in the north of the country following the same methodology. In 45 cross-shore profiles, spaced 2000 m, 130 samples were collected. Three sand samples were taken from each profile, at the beachface, berm and foredune. The mineralogical composition of the clay fraction was analyzed by XRD. Distinct clay mineral associations were identified expressing the relative importance of terrigenous contributions to the beach and dune sediments, stressed by a number of content differences between beachface (illite>> kaolinite, random mixed layers>chlorite), berm (illite>> random mixed layers, kaolinite>chlorite) and foredune deposits (illite>> kaolinite>random mixed layers, chlorite) with significant statistical results. The environmental contrasts exhibited along this coastal sector suggest that this ability might be related with functional factors and not just a product of local constraints.