Open Water Environments Research Articles

Exploring the use of compound-specific carbon isotopes as a palaeoproductivity proxy off the coast of Adélie Land, East Antarctica

Abstract. The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas, where large phytoplankton blooms and drawdown of CO2 occur. Reconstruction of historical primary productivity changes and the associated driving factors could provide baseline insights on the role of these areas as sinks for atmospheric CO2, especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes (δ13C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ∼ 400 years and monitor changes in the concentrations and δ13C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C24 fatty acid δ13C predominantly reflects phytoplankton productivity in open-water environments, while C18 fatty acid δ13C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future palaeoclimate studies.

A Review of Coastal Fog Microphysics During C-FOG

Our goal is to provide an overview of the microphysical measurements made during the C-FOG (Toward Improving Coastal Fog Prediction) field project. In addition, we evaluate microphysical parametrizations using the C-FOG dataset. The C-FOG project is designed to advance understanding of liquid fog formation, particularly its development and dissipation in coastal environments, so as to improve fog predictability and monitoring. The project took place along eastern Canada’s (Nova Scotia and Newfoundland) coastlines and open water environments from August−October 2018, where environmental conditions play an important role for late-season fog formation. Visibility, wind speed, and atmospheric turbulence along coastlines are the most critical weather-related factors affecting marine transportation and aviation. In the analysis, microphysical observations are summarized first and then, together with three-dimensional wind components, used for fog intensity (visibility) evaluation. Results suggest that detailed microphysical observations collected at the supersites and aboard the Research Vessel Hugh R. Sharp are useful for developing microphysical parametrizations. The fog life cycle and turbulence-kinetic-energy dissipation rate are strongly related to each other. The magnitudes of three-dimensional wind fluctuations are higher during the formation and dissipation stages. An array of cutting-edge instruments used for data collection provides new insight into the variability and intensity of fog (visibility) and microphysics. It is concluded that further modifications in microphysical observations and parametrizations are needed to improve fog predictability of numerical-weather-prediction models.

The Influence of Equipment and Environment on Children and Young Adults Learning Aquatic Skills.

Learning aquatic skills is an important component of developing physical literacy in children. Aquatic skills such as floating, swimming and safe entry/exit promote engagement in different water environments and may help preserve lives in an emergency. This scoping review was conducted to evaluate the influence of task constraints (i.e., equipment) and environmental constraints (i.e., physical and social) on how children learn foundational aquatic skills. In developed countries, children are typically taught in swimming pools under direct supervision. It is also not uncommon to see children and infants learning to swim with assistive equipment (e.g., buoyancy aids). However, perhaps surprisingly, the evidence on how and where children learn aquatic skills does not uniformly promote such practices. For example, the use of flotation devices has not been proven to aid skill learning. Some researchers have advocated that children should learn aquatic skills whilst wearing outdoor clothing. One benefit of children wearing clothing is an increased capacity to practice in colder water (such as the ocean, rivers, or lakes). Overall, whilst practitioners often use equipment for various reasons it seems that not all equipment is equally useful in promoting the acquisition of aquatic skills. In less developed countries, with limited access to swimming pools and fewer resources for private instruction, a range of different open water aquatic environments and practices, such as swimming in temporarily flooded areas, have been reported. Such strategies are in urgent demand of further research given that drowning rates in less developed countries around the world exceed those in developed nations. It can be argued that learning in pools does not afford the opportunities to develop the whole range of adaptive skills that may be required in different open water environments such as navigating currents and waves, floating whilst clothed, or making life-saving decisions. Consequently, a shift toward teaching in open water environments has occurred in several countries. This review provides an evidence-base upon which practitioners can design more effective aquatic education programs for children.

Numerical Simulation of the Ice Breaking Process for Hovercraft

A hovercraft can adapt to an ice area, open water, land and other environments, owing to its unique hull structure. It also plays an important role in transporting supplies, rescuing people, breaking ice and conducting other tasks. Ice load prediction is very important for structural safety and navigation of a polar ship, especially in design of air cushion icebreakers or ice breaking platforms. In this paper, based on a simplified circumferential icebreaking pattern, the icebreaking force of the hovercraft operating on the ice sheet at low speed is simulated in a numerical way. Numerical analysis of the icebreaking process with different ice thicknesses and bending strengths are performed. The numerical results are compared with model test data in a time domain for three operating cases. By analyzing the average ice force, the errors between numerical simulation results and model test measurements are less than 30%. The present study is significant for the preliminary design of new icebreaking hovercraft and it assists the operation possibility for existing hovercraft.

Assessment of Alertness and Cognitive Performance of Closed Circuit Rebreather Divers With the Critical Flicker Fusion Frequency Test in Arctic Diving Conditions.

Introduction: Cold water imposes many risks to the diver. These risks include decompression illness, physical and cognitive impairment, and hypothermia. Cognitive impairment can be estimated using a critical flicker fusion frequency (CFFF) test, but this method has only been used in a few studies conducted in an open water environment. We studied the effect of the cold and a helium-containing mixed breathing gas on the cognition of closed circuit rebreather (CCR) divers.Materials and Methods: Twenty-three divers performed an identical dive with controlled trimix gas with a CCR device in an ice-covered quarry. They assessed their thermal comfort at four time points during the dive. In addition, their skin temperature was measured at 5-min intervals throughout the dive. The divers performed the CFFF test before the dive, at target depth, and after the dive.Results: A statistically significant increase of 111.7% in CFFF values was recorded during the dive compared to the pre-dive values (p < 0.0001). The values returned to the baseline after surfacing. There was a significant drop in the divers’ skin temperature of 0.48°C every 10 min during the dive (p < 0.001). The divers’ subjectively assessed thermal comfort also decreased during the dive (p = 0.01).Conclusion: Our findings showed that neither extreme cold water nor helium-containing mixed breathing gas had any influence on the general CFFF profile described in the previous studies from warmer water and where divers used other breathing gases. We hypothesize that cold-water diving and helium-containing breathing gases do not in these diving conditions cause clinically relevant cerebral impairment. Therefore, we conclude that CCR diving in these conditions is safe from the perspective of alertness and cognitive performance.

Acoustic telemetry detection probability and location accuracy in a freshwater wetland embayment

BackgroundIn recent years, large-scale acoustic telemetry observation networks have become established globally to gain a better understanding of the ecology, movements and population dynamics of fish stocks. When studying a species that uses different habitats throughout its life history difficulty may arise where acoustically suboptimal habitats are used, such as shallow, vegetated areas. To test the feasibility of active tracking in these acoustically suboptimal habitats, we quantified detection probability and location error as a function of several environmental variables with two transmitter types in a shallow freshwater embayment.ResultsWhen placed in nearshore areas (< 1 m deep), the higher-powered transmitter (158 dB) had significantly greater detection probability than the lower-powered transmitter (152 dB). For both transmitter types, detection probability declined at 200 m; however, at the 100 m distance the higher-powered transmitter had greater than 50% detection probability per ping cycle (50.4%) while the lower-powered transmitter was substantially less (29.4%). Additionally, detection probability increased when the transmitter was deployed within sparse, senescent Phragmites spp. vegetation (14%). Estimated positional accuracy of transmitters deployed at known locations (location error) was variable (error range: 13–259 m), and was generally higher for the more powerful transmitter. Location error was minimized when the lower-powered transmitter was located near softened shoreline areas compared to near man-made armored shorelines (i.e., rip-rap).ConclusionWhile benefits exist for maximizing transmitter power (e.g., increased detection range in open-water environments), use of a lower-powered transmitter may be advantageous for active tracking specific locations of fish inhabiting shallow water environments, such as in estuarine tidal marshes and shallow wetlands. Thus, when planning acoustic telemetry studies, researchers should conduct site-specific preliminary detection probability/location error experiments to better understand the utility of acoustic telemetry to investigate fish movements in acoustically suboptimal conditions.

Coastal-Fog Microphysics Using In-Situ Observations and GOES-R Retrievals

The objective of this work is to evaluate GOES-R (Geostationary Operational Environmental Satellites-R series) data-based fog conditions which occurred during the C-FOG (Toward Improving Coastal Fog Prediction) field campaign. The C-FOG campaign was designed to advance understanding of fog formation, development, and dissipation over coastal environments to improve predictability. The project took place along coastlines and open water environments of eastern Canada (Nova Scotia, and the Island of Newfoundland) during August−October of 2018 where environmental conditions play an important role for late season fog formation. During the C-FOG field campaign, coastal instruments were mainly located at the Ferryland supersite, Newfoundland, with two main sites, and five satellite sites, as well as on the Research Vessel Hugh R. Sharp. Key in-situ measurement instruments included microphysical, meteorological, radiation, and aerosol sensors. A fog spectral probe was used for measuring droplet spectra from 1–50 µm at the Ferryland supersite. A laser precipitation monitor with 100 µm to 10 mm size range and an optical particle counter with 0.3–17 µm at 16 spectral channels provided information for fog and drizzle discrimination. Remote sensing platforms, e.g. profiling microwave radiometer, ceilometer, microwave rain radar, lidar, meteorological towers, tethered balloons, and GOES-R products for fog coverage, and droplet size and liquid water path) were used to evaluate fog over horizontal and vertical dimensions. Results suggest that effective radius, phase, liquid water path, and liquid water content values obtained from GOES-R and the profiling microwave radiometer are comparable to ground-based in-situ observations. It is concluded that integration of observations and nowcasting products may help improve short-term local fog predictions.

Jurassic planktic foraminifera from the Polish Basin

Abstract. Jurassic (Bathonian–Oxfordian) planktic foraminifera from the epicontinental strata of the Polish Basin have been investigated. The palaeoecology, palaeobiogeography, and biostratigraphical potential of the recorded taxa are discussed. Four species are recorded: Conoglobigerina helvetojurassica (Haeusler, 1881), Globuligerina balakhmatovae (Morozova, 1961), G. bathoniana (Pazdrowa, 1969), and G. oxfordiana (Grigelis, 1958). This assemblage is probably the most diverse of those described to date from the epicontinental areas of Europe. The recorded taxa are thought to represent three different ecological morphotypes. The clear relationship between transgressive–regressive facies and the palaeobiogeography of the recorded planktic foraminifera indicates a morphotype-related depth–distribution pattern in which small, simple, globular-chambered morphotypes occupied shallow waters whereas slightly larger, more complex forms, or those with hemispherical chambers, inhabited deeper and more open-water environments.

Recolonization of lake whitefish river spawning ecotypes and estimates of riverine larval production in Green Bay, Lake Michigan

Lake whitefish (Coregonus clupeaformis) within the waters of Green Bay, Lake Michigan have recently shown a substantial increase in abundance. Furthermore, after over 100 years of extirpation, adult lake whitefish are found spawning within major Wisconsin tributaries to Green Bay. Many knowledge gaps still exist with respect to the chronology of adult river migrations, including the physical characteristics of upstream habitats selected for reproduction and the extent of larval production by these riverine ecotypes. Here, we use hydroacoustic imaging along with egg and larval surveys to evaluate this novel riverine spawning in 2017 and 2018. Highest abundance of adults was observed in the month of November as temperatures declined below 8 °C. Spawning areas consisted of cobble substrates, and site-specific fish densities were primarily correlated with river flows between 0.3 and 1.0 m/s, with specific values varying by tributary and year. Locations of egg deposition mirrored areas of high observed fish densities. Larval production was documented on each tributary using active trawl ichthyoplankton sampling, and larvae were observed outmigrating to open water environments. We estimated tributaries produced 452,000 larvae in 2017 and 721,000 larvae in 2018. To our knowledge, this represents the first documentation of successful lake whitefish larval production from Green Bay tributaries and suggests tributary spawning populations contribute to the greater abundance of lake whitefish observed in recent years.

A maritime archaeological conservation citizen science programme for individual benefit and good public outcomes: GIRT Scientific Divers

ABSTRACT In Australia and New Zealand, a citizen science approach is being trialled to bring spatial scale and longevity to underwater cultural heritage monitoring programmes which are beyond the resourcing capacity of management agencies. Gathering Information via Recreational and Technical (GIRT) Scientific Divers is a no-impact maritime archaeological conservation-focussed citizen science programme that trains members to systematically document observable physical and natural features of underwater cultural heritage, in an open sea water environment, to understand the condition of a site and facilitate its protection and management. A key objective of GIRT is to encourage interested people, businesses, and groups to have an active and positive public (and community) archaeology role. This paper outlines GIRT, its methodology and andragogical teaching approach. Examples noting the significant effort required by members to participate, the need to emphasize the site survey’s scalability of activity, and the value of having included marine science in the methodology are highlighted.

Visual adaptation of opsin genes to the aquatic environment in sea snakes

BackgroundEvolutionary transitions from terrestrial to aquatic life history cause drastic changes in sensory systems. Indeed, the drastic changes in vision have been reported in many aquatic amniotes, convergently. Recently, the opsin genes of the full-aquatic sea snakes have been reported. However, those of the amphibious sea snakes have not been examined in detail.ResultsHere, we investigated opsin genes and visual pigments of sea snakes. We determined the sequences of SWS1, LWS, and RH1 genes from one terrestrial, three amphibious and four fully-aquatic elapids. Amino acid replacements at four and one spectra-tuning positions were found in LWS and RH1, respectively. We measured or predicted absorption of LWS and RH1 pigments with A1-derived retinal. During their evolution, blue shifts of LWS pigments have occurred stepwise in amphibious sea snakes and convergently in both amphibious and fully-aquatic species.ConclusionsBlue shifted LWS pigments may have adapted to deep water or open water environments dominated by blue light. The evolution of opsins differs between marine mammals (cetaceans and pinnipeds) and sea snakes in two fundamental ways: (1) pseudogenization of opsins in marine mammals; and (2) large blue shifts of LWS pigments in sea snakes. It may be possible to explain these two differences at the level of photoreceptor cell composition given that cone and rod cells both exist in mammals whereas only cone cells exist in fully-aquatic sea snakes. We hypothesize that the differences in photoreceptor cell compositions may have differentially affected the evolution of opsins in divergent amniote lineages.

Development of Innovative Solutions for Intelligent Inspection of Products of Additive Manufacturing for Navy Supply

Using of 3D printed spare parts for Navy supply supported by mentioned inspection meets the requirement for enhancing the logistic performance by provide to military end-users possibilities to produce spare parts using additive manufacturing solutions, particularly in the context of overseas operations, that can be easily presented with several examples. But with application of additive manufacturing in naval operations to product different objects in a variety of materials in an open water environment, we need to start with development of innovative solutions for intelligent inspection of products of selective laser melting from metallic powders is a topic of great importance in nowadays if we talk about real strategies in logistic support including overseas naval outposts support equipment and the reverse engineering of obsolescent parts such as many of those that could be found on the perspective sea platforms with particular focus on maritime littoral and high sea areas—demonstrate advantages of additive manufacturing.

#biteme: Considering the Potential Influence of Social Media on In-Water Encounters with Marine Wildlife

Over the past three decades, interacting with wildlife as a tourism activity has grown significantly and has transformed from a relatively rare experience into a mainstream tourism product. Tourism opportunities to watch, photograph, and otherwise interact with animals in their natural environment have grown to include a range of species and settings, including in the sea. Close encounters with marine wildlife are facilitated by a wide range of commercial operators, and many include and promote a strong adventure component. This article provides a consideration of the issues of risk and the emerging role of the use of social media in marine wildlife tourism experiences. While the concept of ecotourism has been widely explored in wildlife tourism research, the inherited risk involved in these activities has received little attention. This is particularly the case regarding interactions with potentially dangerous wildlife in open-water environments. This aspect warrants exploration in the context of the growth of wildlife photography/videography and sharing via social media platforms, which frequently display close encounters with animals in dangerous scenarios for both people and wildlife involved.

Teaching Foundational Aquatic Skills to Children in Open Water Environments

Learning to swim in a swimming pool might not prepare water competence sufficiently for different aquatic environments. The aim of this study was to assess the effectiveness of teaching children water safety knowledge and skills in open water environments (i.e., harbor, river, and surf). The aquatic knowledge and skills of 98 children (7-11 years old) were tested in a swimming pool before, immediately after, and three months after receiving a three-day intensive education program. At pre-test, typically fewer than 50% of children achieved a high level of water safety competence. After the program, competency in each of the six tasks assessed had increased with up to 80% of participants completing the tasks unassisted. Three-month retention of these skills was generally high (i.e., competency levels were either maintained or improved). A key challenge for future research will be to untangle the influences of maturation, order effects, and the open water education.

Education and transfer of water competencies: An ecological dynamics approach

To cope in various aquatic environments (i.e. swimming pools, lakes, rivers, oceans), learners require a wide repertoire of self-regulatory behaviours such as awareness of obstacles and water properties, floating and moving from point to point with different strokes, decision making, emotional control and breathing efficiently. By experiencing different learning situations in stable indoor pool environments, it is assumed that children strengthen aquatic competencies that should be transferable to functioning in open water environments, where prevalence of drowning is high. However, this fundamental assumption may be misleading. Here, we propose the application of a clear, related methodology and theoretical framework that could be useful to help physical education curriculum specialists (re)shape and (re)design appropriate aquatic learning situations to facilitate better transfer of learning. We discuss the need for more representativeness in a learning environment, proposing how the many different task and environmental constraints on aquatic actions may bound the emergence of functional, self-regulatory behaviours in learners. Ideas in ecological dynamics suggest that physical educators should design learning environments that offer a rich landscape of opportunities for action for learners. As illustration, three practice interventions are described for developing functional and transferrable skills in indoor aquatic environments. It is important that aquatic educators focus not just upon ‘learning to swim’, but particularly on relevant transferable skills and self-regulatory behaviours deemed necessary for functioning in dynamic, outdoor aquatic environments.

Using Large-Aperture Scintillometer to Estimate Lake-Water Evaporation and Heat Fluxes in the Badain Jaran Desert, China

Accurate estimation of evaporation (E0) over open water bodies in arid regions (e.g., lakes in the desert) is of great importance for local water resource management. Due to the ability to accurately determine sensible (H) and latent (LE) heat fluxes over scales of hundreds to thousands of meters, scintillometers are more and more appreciated. In this study, a scintillometer was installed on both sides of the shore over the Sumu Barun Jaran Lake in the Badain Jaran Desert and was applied to estimate the sensible and latent heat fluxes and evaporation to be compared with the data of an evaporation pan and an aerodynamic model. Based on the field data, we further analyzed the seasonal differences in the flux evaluation using water temperature at different depths at half-hour and daily time scales, respectively. The results showed that in cold seasons, values of H were barely affected by the changes of shallow water temperature, whereas in hot seasons, the values were changed by 20%–30% at the half-hour time scale and 6.2%–18.3% at the daily time scale. In different seasons, shallow water temperature at different depths caused changes in the range of 0%–20% of LE (E0). This study contributes to a better understanding of uncertainties in measurements by large-aperture scintillometers in open-water environments.

Exploratory Analysis of Treading Water Coordination and the Influence of Task and Environmental Constraints.

The radical embodied cognition approach to behavior requires emphasis upon how humans adapt their motor skills in response to changes in constraint. The aim of this exploratory study was to identify how the typical coordination patterns used to tread water were influenced by constraints representative of open water environments. Twenty-three participants were measured while treading water (TW) in a swimming flume in four conditions: (1) in still water, wearing a bathing suit (baseline); (2) wearing typical outdoor clothing (clothed); (3) with an additional cognitive task imposed (dual task); and (4) against a changing current (flow). Mixed methods kinematic analysis revealed four different TW coordination patterns were used across the conditions. The four TW patterns used represent a hierarchy of expertise in terms of the capacity to generate continuous lift forces, where pattern 1 (the lowest skill level) involved predominantly pushing and kicking limb movements (N = 1); pattern 2 was a movement pattern consisting of legs pushing/kicking and arms sculling (N = 7); pattern 3 was synchronous sculling of all four limbs (N = 6); and pattern 4 was the “eggbeater kick” (the highest skill level), with asynchronous sculling movements of the legs (N = 9). The four TW patterns were generally robust to the modified constraints. The higher skilled patterns (i.e., patterns 3 and 4) appeared to be the most stable coordination patterns. These results suggest that learning to perform more complex patterns to tread water might be an asset to survive in life-threatening situations.

Geochemical attributes for source rock and palaeoclimatic reconstruction of the Auranga Basin, India

The present study aims to investigate the source and palaeoenvironmental conditions prevailed during the deposition of the Lower Permian shales of the Auranga Basin located at western flank of the Damodar valley, India. Both organic and inorganic geochemistry have been applied as tools to accomplish the objectives of this investigation. The n-alkane distribution within the samples reveals the dominance of the intermediate chain length n-alkanes over the short chain as well as long chain length homologues, possibly implying the organic matter derivation from the ferns, sphagnum moss, gymnosperms and/or aquatic plants. The intermediate chain n-alkane concentration along with its relations with the preference indices of odd to even carbons and proxy ratio as well as with average chain length may suggest the submergent aquatic plant communities as principle contributors of organic materials to the peatland. The presence of short chain length alkanes with pentacyclic triterpenoids may indicate the microbial organic matter input. The complete absence of <n-C16 alkanes and baseline humps in the pentacyclic triterpenoid chromatograms may indicate the influence of biodegradation of the organic matter in the shale samples. The pristane to phytane ratio (0.08–4.66) and the relation between pristane/n-C17 and phytane/n-C18 may imply transitional redox condition within the mire. The pristane/n-C17 ratio (0.08–1.24) may indicate the alternations of open water and swampy environments. The chemical weathering indices calculated from major elemental oxides may infer moderate to strong weathering due to reasonable period of precipitation during a wet spell. The selective trace element ratios and the palaeoclimatic factor (0.60–1.73) may, additionally, suggest high atmospheric humidity and consequent heavy precipitations that flourished the aquatic plants, which would have dominantly supplied the organic detritus in the peatland. In complementary, the hopanoid ratios, especially, the 22S/(22S + 22R) homohopane ratio may mark that the organic matter within the Auranga shales is in immature to early maturity phase for oil generation. Moreover, the combined mean random vitrinite reflectance and the thermal maturity parameter obtained from the Rock Eval data may indicate oil potential of these shales.

Underwater object localization using compressive sensing

In this paper, we propose a technique to localize a moving submerged object with a sparse measurement using a hydrophone array. We used a natural muddy pond bottom with 9 m length, 5.5 m width, and 2 m depth. First, we measured the pond impulse response to identify the sound propagation characteristics. In the second phase namely static direction of arrival (DOA), the underwater speaker was placed at half-circle positions with respect to the array to simulate the underwater object trajectory, 0 deg, 30 deg, 60 deg, 90 deg, 120 deg, 150 deg, and 180 deg, respectively. The sound generated by a four-blade propeller submarine toy was measured to track its trajectory as a dynamic DOA measurement. The measured data were transformed into discrete cosine transform coefficients and reconstructed sparsely by using the basis pursuit algorithm. Based on the estimated incident angle and time delay, the reconstructed measurements were then compared to full dictionary measurement. The results showed that the error angle of the origin deviated about 2.5 deg with half of the measured data were lost. This may suggest that the sound propagation was degraded due to bottom reverberation and scatterers. Currently, we do a similar measurement in an open shallow water environment to eliminate the reverberation.

Baseline information on prokaryotic and microeukaryotic plankton communities inside and outside of Indonesian marine lakes

Marine lakes represent a unique and globally rare aquatic environment characterised by lower salinities and pH and higher temperatures than the surrounding open water environment. Here we provide baseline data on planktonic communities of Archaea, Bacteria and microeukaryotes inside and outside (open water habitat) of three marine lakes (Kakaban, Haji Buang and Tanah Bamban) in the Berau region of Indonesia. Compositional variation was highly congruent with the major axis of variation separating open water from marine lake samples for all three domains. Planktonic Archaea mainly consisted of OTUs assigned to Euryarchaeota that were closely related to organisms in Genbank previously obtained from seawater samples. The majority of archaeal OTUs were most abundant in open water habitat with a few OTUs abundant in all habitats. Most bacterial sequences were assigned to Proteobacteria, Cyanobacteria and Bacteroidetes with the percentage of Cyanobacteria highest in two of the marine lakes and lowest in the remaining lake (Tanah Bamban). In contrast to Archaea, there were a number of bacterial OTUs that were markedly more abundant in marine lake habitat. Most microeukaryote sequences were assigned to the Alveolata, Stramenopiles, Opisthokonta, Archaeplastida and Hacrobia. As was the case with Bacteria, a number of abundant microeukaryote OTUs were more abundant in marine lake habitat. Our results thus indicate similar compositional responses to the environmental conditions in marine lake habitat across the major domains of life and point to marine lakes harbouring distinct microbial communities.