Narrow Strait Research Articles

Modelling of underwater noise emissions by ships in Klaipėda Strait, Lithuania

One of the United Nations Sustainable Development Goals regarding “conservation and sustainable use of the oceans, seas, and marine resources” emphasizes the urgency of eliminating harmful effects on the sea and its biota, where the role of anthropogenic activities is crucial. The global trend of merchant shipping is increasing, thus enlarging underwater noise levels. As a result, greater noise can harm aquatic animals in their habitats. In the Baltic Sea, the underwater sound pressure levels are now being evaluated utilizing noise measurement, modelling, and mapping. In areas such as narrow ship passages, namely lagoons, channels, or straits, the ambient underwater noise modelling becomes very complex, even though these EU inland waters are regarded by legislation as part of the marine basin. For instance, the Klaipėda Channel (Klaipėda Strait), connecting the Baltic Sea and the Curonian Lagoon, is regarded by the national Lithuanian legislation as part of marine waters, where the environmental status should be evaluated according to the EU Maritime Strategy Framework Directive. In this narrow channel, an alternative to the modelling of ambient sound pressure levels can be applied to understand the long-term trends of vessel-sourced noise emissions. In this paper, an example of application of ship noise emission modelling for a narrow Klaipėda Harbour area is presented, along with the results obtained throughout 2015–2017. The modelled noise levels in the harbour area reached the median levels of 112.5 dB in 2015 and 102.6 dB re 1 µPa2 in 2017. The maximum emitted instantaneous sound pressure levels by ships reached 173.7 dB in 2015 and 179.4 dB re 1 µPa2 in 2017 in the area of interest.

Comparison of Simulated and Observed Current Velocities in Karimata and Gaspar Straits

Karimata and Gaspar Straits were the connector between the South China Sea and Indonesian Seas, which played a role in transporting the Indonesian Through Flow. The current velocities in both straits were studied by comparing outputs from the INDO12 physical ocean model simulation against observation results from the South China Sea-Indonesian Seas Transport Exchange (SITE) program. In general, the magnitudes of the zonal and meridional model current velocities are weaker than observations. Notably, the B1 and B4 moorings show uncertain model values most of the time. It is understandable considering that B1 and B4 moorings are located in a narrow strait (Gaspar Strait), near the coasts. On the contrary, B2 and B3 moorings show comparable magnitude to the two zonal and meridional components' observations Keywords: Karimata Strait, Current Velocities, INDO12, SITE Program

A coupled ecohydrodynamic model to predict algal blooms in Lake Titicaca

Lake Titicaca is home to a unique high-altitude ecosystem that is suffering from increasing anthropogenic pressures. It experienced its first major algal bloom in March–April 2015 that had devastating consequences in the southern shallow lake basin. Such events are expected to intensify in the future and call for a more active and quantitative management of the lake and its watershed. In this paper we describe a coupled ecohydrodynamic model to predict the lake’s water quality and, more particularly, the risk of harmful algal blooms. We have coupled a nitrogen-phytoplankton-zooplankton-detritus (NPZD) ecosystem model to the unstructured-mesh 3D hydrodynamic model SLIM. Our high-resolution multi-scale model explicitly represents the exchanges between the two basins composing the lake, through the narrow Strait of Tiquina. This allowed us to study the biophysical processes driving the entire lake over the period of January 2014 to May 2015. The model has been validated against temperature profiles at several locations throughout the lake. It correctly reproduces the seasonal temperature variations that drive the lake stratification and impact the vertical distributions of phytoplankton. Our model was able to replicate the space–time dynamics of the March–April 2015 algal bloom similarly to what was observed on satellite imagery. We believe that our multi-scale ecohydrodynamic model is a promising tool to complement field observations and hence support water management in the lake and its watershed.

Paleoenvironmental implications of Sr and Nd isotopes variability over the past 48 ka from the southern Sea of Japan

Millennial scale variations of terrigenous provenance in marine realm are closely related to regional environment and climate changes. Therefore, a wealth of information of past environment and climate can be constrained via fingerprinting sediment provenance. The Sea of Japan is a unique marginal sea in the North Pacific due to its high sill and distinct thermohaline circulation. The modern hydrography in the Sea of Japan is mainly affected by the East Asian Monsoon and Tsushima Warm Current, one branch of the Kuroshio Current. The Sea of Japan communicates with neighboring seas through four shallow and narrow straits, indicating great effects of global eustatic sea level change on its environment over glacial-interglacial cycles. Here we examine the terrigenous provenance in fine-grained fraction (<63 μm) of core KCES1, located near one end of the Tsushima Strait of the Sea of Japan over the last 48 ka, using radiogenic isotopes of strontium (Sr) and neodymium (Nd). Our data suggest that the terrigenous provenance in core KCES1 was mainly derived from the Yangtze River after 7 ka and a mixture of Yangtze and Yellow Rivers during the last glacial and deglacial periods. Notably, pronounced negative excursions of εNd values at HS1 were attributed to minor additions of unradiogenic Nd contribution from China-Korea cratonic hinterland. A binary mixing model further reveals that >85% terrigenous material is derived from the Yangtze and Yellow Rivers over the last 48 ka. Moreover, abrupt variations in sediment provenance occurred at ~18 ka and ~ 7 ka, which coincide with variations in oceanic surface circulation and deep ventilation recorded in the Sea of Japan. We suggest that paleo-Tsushima Warm Current invaded into the Sea of Japan with reopening of the Tsushima Strait at HS1 and the Tsushima Warm Current substantially entered the Sea of Japan after 7 ka due to intensified Kuroshio Current and rising eustatic sea level. The inflow of Tsushima Warm Current gives rise to a range of changes in surface hydrography, deep ventilation, ecological communities and productivity and sediment texture. The combination of fluxes of paleo-rivers and the intensity of Kuroshio Current, which are closely tied to the eustatic sea level and the East Asian Monsoon, plays a key role in controlling the variations in sediment provenance in the Ulleung Basin. Our study provides unique insight into the tight coupling between changes in sediment provenance and oceanic environment over the last 48 ka in the Sea of Japan.

Fjordic Lagoons of the Barents Sea as Models for Study of the Dynamics of Coastal Communities with Alien Red King Crab (Paralithodes camtschaticus, Decapoda, Lithodidae)

Benthic communities of the semi-isolated deep fjordic Linjalampi and Sisajarvi lagoons in the apex part of Ambarnaya Bay, Varanger fjord, Barents Sea, are affected by the limited water exchange and wave action in combination with other abiotic and biotic factors. Among the biotic factors, the presence of a numerous group of red king crab (Paralithodes camtschaticus) that naturalized in the southern part of the Barents Sea in the second half of the 20th century may play a particularly important role. The median density of juvenile and adult crabs in the lagoons (42.5–52 specimens/1000 m2 in most years of observation) is comparable to their density in the neighboring open parts of the Varanger fjord. A narrow and shallow strait connecting the lagoons with the sea may restrict crab migrations between these habitats. Thus, adult crabs are present in the lagoons in the seasons when they migrate from the coast to greater depths in their usual habitats. The food chains starting from phytoplankton and macrophytes to benthic predators, red king crabs, spider crabs (Hyas araneus), and hermit crabs (Pagurus pubescens) have been studied using stable isotope analysis. The trophic level of adult king crabs in the lagoons (2.88) is lower than that of both spider crabs (3.16–3.42) and those king crabs that occur in the open part of the coastal area (3.44). This indicates differences in the feeding habits of crabs in the lagoons and in the open coastal waters. The food chain kelp–sea urchins–red king crabs typical for the coastal zone in the Barents Sea is not expressed in the food web of the lagoons. The low abundance and distribution patterns of sea urchins may be due to their consumption by red king crabs over a long period. Although fjordic Linjalampi and Sisajarvi lagoons are full marine water bodies, they are similar to continental lakes in some characteristics. In particular, the conditions in the lagoons make them convenient models for the study of the long-term dynamics of communities and ecosystems.

Combined Effects of Tidal Mixing in Narrow Straits and the Ekman Transport on the Sea Surface Temperature Cooling in the Southern Indonesian Seas

AbstractAlthough the SST cooling events around the Lesser Sunda Islands (LSIs), which contribute to the seasonal variation of SST in the southern Indonesian Seas, are thought to be controlled by tidal mixing, the distribution of tidal mixing was highly idealized in previous studies. This study reinvestigates the mechanisms of such SST cooling events using MITgcm, which incorporates the realistic distribution of tidal mixing. The observed SST variability is well reproduced in the numerical experiment; SST is largely reduced along the northern (or southern) coast of the LSIs during austral summer (or winter). Particle tracking suggests that the narrow tidal straits between the LSIs, where well‐mixed waters are produced by vigorous tidal mixing, play a key role in controlling the SST cooling. During austral summer, the cold SST signal of well‐mixed waters propagates both northward and southward from the narrow straits as baroclinic Kelvin waves. On the northern side of the LSIs, in particular, coastal upwelling caused by the northwest monsoon raises the background thermocline, which affects the propagation of baroclinic Kelvin waves such that the accompanying cold SST signal becomes much enhanced compared with that on the southern side of the LSIs. During austral winter, in contrast, the Ekman transport enhances southward through‐strait flow so that baroclinic Kelvin waves can propagate only southward affecting the SST on the southern side of the LSIs. This demonstrates the importance of the combined effects of tidal mixing in narrow straits and the Ekman transport on the SST cooling in the southern Indonesian Seas.

New findings on palynofacies characteristics of semi-enclosed deep-sea environments in the East Sea over 2\xa0million years

Phytoclasts in the form of plant debris in terrestrial sediments can be transported by water to distant areas because they are lighter than inorganic particles. The semi-enclosed East Sea, which is connected by narrow straits to other seas, is adjacent to continental shelves that are the source area of terrestrial sediment flowing into the East Sea. These shelves alternated repeatedly between terrestrial and marine environments as a result of eustatic sea-level changes during the Late Quaternary. Palynofacies analyses of the IODP Exp. 346 U1430 core, located in the Eastern South Korea Plateau (ESKP) of the East Sea, have revealed changes in the size and concentration of phytoclasts associated with glacial–interglacial cycles. These changes are generally negatively correlated with the global sea-level curve, and their anti-phase cycles with high amplitude are clearly evident during the last ca. 750 ka with the geotectonic stabilization period. In particular, several coarse-grained phytoclasts were observed during the glacial period, including the Last Glacial Maximum (LGM). These findings suggest that the concentration and size of phytoclasts flowing into the East Sea were influenced by changes in the distance of the source area, depending on the water depth of the strait and nearby shelves owing to sea-level changes in tandem with glacial–interglacial cycles and geotectonic events.

Cold Water Upwelling Near the Anadyr Strait: Observations and Simulations

AbstractAnadyr Strait, located at the northernmost reaches of the Bering Sea, influences pan‐Arctic climate through processes occurring in the strait as the Siberian Coastal Current carries water from the subpolar North Pacific Ocean into the western Arctic Ocean. A sharp sea surface temperature front near the Anadyr Strait segregates a tongue‐shaped mass of warm water from areas of cold‐water upwelling proximate to the Siberian coast. To clarify dynamical processes in this region, we conducted shipboard observations through and near the Anadyr and Bering straits during the summers of 2017 and 2018. Microstructure measurements show enhanced turbulence near the sea floor as strong throughflow occurs in the narrow straits. Direct observations of ocean currents indicate that the semidiurnal barotropic tide partly contributes to the near‐bottom currents driving mixing. Frictional effects accompanying the barotropic current are examined using a three‐dimensional regional model. Bottom friction produces a westward Ekman current in the bottom boundary layer, which then causes upwelling of underlying cold water on the western (Siberian) side of the Anadyr Strait. Secondary circulation across the strait is also maintained by the near‐surface eastward velocity, which is established by the steep slope of the main thermocline.

Tidal Currents Detected in Kraken Mare Straits from Cassini VIMS Sun Glitter Observations

Abstract We present Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of sun glitter—wave-induced reflections from a liquid surface offset from a specular point—on Kraken Mare. Sun glitter reveals rough sea surfaces around Kraken Mare, namely the coasts and narrow straits. The sun glitter observations indicate wave activity driven by the winds and tidal currents in Kraken Mare during northern summer. T104 Cassini VIMS observations show three sun glitter features in Bayta Fretum indicative of variegated wave fields. We cannot uniquely determine one source for the coastal Bayta waves, but we lean toward the interpretation of surface winds, because tidal currents should be too weak to generate capillary–gravity waves in Bayta Fretum. T105 and T110 observations reveal wave fields in the straits of Seldon Fretum, Lulworth Sinus, and Tunu Sinus that likely originate from the constriction of tidal currents. Coastlines of Bermoothes and Hufaidh Insulae adjoin rough sea surfaces, suggesting a complex interplay of wind-roughened seas and localized tidal currents. Bermoothes and Hufaidh Insulae may share characteristics of either the Torres Strait off Australia or the Åland region of Finland, summarized as an island-dense strait with shallow bathymetry that hosts complex surface circulation patterns. Hufaidh Insulae could host seafloor bedforms formed by tidal currents with an abundant sediment supply, similar to the Torres Strait. The coastlines of Hufaidh and Bermoothes Insulae likely host ria or flooded coastal inlets, suggesting that the Insulae may be local peaks of primordial crust isolated by an episode of sea-level rise or tectonic uplift.

The Role of Weather during the Greek–Persian “Naval Battle of Salamis” in 480 B.C.

The Battle of Salamis in 480 B.C. is one of the most important naval battles of all times. This work examines in detail the climatically prevailing weather conditions during the Persian invasion in Greece. We perform a climatological analysis of the wind regime in the narrow straits of Salamis, where this historic battle took place, based on available station measurements, reanalysis and modeling simulations (ERA5, WRF) spanning through the period of 1960–2019. Our results are compared to ancient sources before and during the course of the conflict and can be summarized as follows: (i) Our climatological station measurements and model runs describing the prevailing winds in the area of interest are consistent with the eyewitness descriptions reported by ancient historians and (ii) The ancient Greeks and particularly Themistocles must have been aware of the local wind climatology since their strategic plan was carefully designed and implemented to take advantage of the diurnal wind variation. The combination of northwest wind during the night and early morning, converging with a south sea breeze after 10:00 A.M., formed a “pincer” that aided the Greeks at the beginning of the clash in the morning, while it brought turmoil to the Persian fleet and prevented them to escape to the open sea in the early afternoon hours.

Faulting within the San Juan–southern Gulf Islands Archipelagos, upper plate deformation of the Cascadia subduction complex

Abstract The San Juan–southern Gulf Islands Archipelago of Washington State, USA and western Canada is located on the upper plate of the Cascadia subduction zone, in the forearc between the trench and volcanic arc. Onland and island investigations show many faults within the region that primarily represent old, inactive faults associated with transport, subduction and accretion of tectonostratigraphic terranes. However, until recently little geologic investigation and mapping have been done in the offshore. From these narrow straits, channels and sounds we have collected and interpreted high-resolution multibeam echosounder bathymetric data, 3.5 kHz sub-bottom and Huntec seismic-reflection profiles, and piston-cores to identify and date recently active faults. Previous studies by us focused on the earlier recognized active Devils Mountain fault zone that bounds the southern part of the Archipelago and the recently reported newly mapped active Skipjack Island fault zone that bounds the northern part. These transcurrent fault zones appear to be deforming and rotating the Archipelago. We concentrate on the unique deformation occurring within the seaways to determine the relationship and styles of faulting associated with these active bounding fault zones and relate the fault geometry and kinematics to one other subduction complex, the New Hebrides island arc of Vanuatu.

SEASONAL WATER SALINITY VARIABILITY OF THE MIDDLE PART OF THE SUKHOI LIMAN (BLACK SEA)

Problem Statement and Purpose. The middle part of Sukhoi liman is connected to its lower part (including port area) by a narrow strait. Water exchange between the parts is limited by a pontoon ferry. The salinity of water masses determines by many economic and biological processes in the liman and their parts as well. The salinity of the Sukhoi liman water masses has been mostly studied in the lower part. The middle part was studied only in summer. Seasonal variability in the salinity of the middle part is unexplored. Annual salinity rates there changed depending on a water area from 12.8 ‰ to 15.6‰. As for mineralization the studied water masses are brackish (1–25‰). The main goal of the article is to determine current seasonal changes in the salinity of the Sukhoi liman middle part.Data &amp; Methods. This study is based on results of the laboratory treatment of water samples collected during shore-based stationary exploration from May 2019 to Janu­ary 2020. Water samples were taken every last day of the month, close to noon when the temperature of water and its level stabilized. In June 2019, the salinity of the water was examined at sections in the northern, central and southern parts of the water body under investigation. Water samples were taken at 0.1H horizons from the surface and near the bottom. 10 samples were taken at the observation point and 12 at the sections. Water salinity was determined by the areometric method, not later than in two days after sampling. Data about meteorological conditions during the observation period (air temperature, wind speed and direction) are obtained from www.rp5ua.Results. Seasonal variability in the salinity of water masses has a number of distinc­tive features. The spatial distribution of the salinity of the middle part of the Sukhoi liman is homogeneous, with maximal values in the central part of the water body and decreasing towards the upper and lower parts. The salinity varies from 10.4‰ up to 15.3‰ per year: maximum values are observed in summer and autumn, the salinity is minimal in spring and the salinity is average moderate in winter. The salinity of water masses is influenced by meteorological conditions, mainly air temperature and wind. Further observations of the salinity and features of the hydrological regime of the mid-water area have practical and scientific significance for the development of the Sukhoi liman use, and for evaluating how the construction of a road bridge influ­ences to the natural resource. It is also scientifically valuable to study the patterns of transformation of water masses when they move from the sea to different parts of the liman.

Ibadi Jerba: surviving the early Ḥafṣids (13–14th centuries)

ABSTRACT The Ibadi-majority Island of Jerba, off the coast of modern-day Tunisia, faced several external threats from the 13th–14th centuries. This article explores how the closed social system of the Ibadis in the island of Jerba survived the powerful Hafsids in Tunis as well as attacks by Christian European powers. It explores the different campaigns by both Sunni-Hafsid and Sicilian-Norman armies looking to establish a strategic fortification in Jerba. We also look at the circumstances that led to the Hafsid campaign to the island by the early 14th century. Moreover, we examine the Sunni-Hafsid perception of Jerba as a ‘rogue’ community, one that should be weakened and absorbed into the homogenous Sunni-Maliki Maghribi domain. Despite these many threats, the Ibadi community of Jerba survived threats from across the narrow strait separating it from North Africa to across the Mediterranean.

Marine debris on two Arctic beaches in the Russian Far East

In August 2005, marine debris was counted on two Arctic beaches in the Russian Far East. On the north coast of the Chukchi Peninsula east of Kolyuchin Bay, a beach stretch of ca. 2.4 km held a total of 736 items, 0.024 items m‑2, while no more than 0.0011 items m‑2, 12 items in total, were found on a beach stretch of ca. 1.2 km on southern Wrangel Island. The likely explanation for this difference is that the area around the mainland beach is ice-free for a longer period each year, but a contributing factor may be that late spring ice movement removed plastic from the beach on Wrangel Island. The language on the few items with identifiable labels was for the most part Russian or English, making the Chukchi Sea a possible source region. Beaches at the same latitude in the Atlantic may hold more debris on account of the higher human population density, more shipping and transport of floating debris unhindered by a narrow strait that is ice-covered much of the year. Fishing gear blown across the tundra is suggested as a potential threat to reindeer and other terrestrial wildlife.

The Impact of Winter Storms on Sediment Transport Through a Narrow Strait, Bohai, China

AbstractThe Yellow River is one of the most significant sources of terrestrial sediment to the global seas, and the Bohai Strait is the only pathway that delivers Yellow River‐derived sediments from the shallow Bohai Sea to the Yellow Sea. To investigate sediment transport processes through the strait under the influence of storms (strong northerly winds) that frequently occur in winter, we deployed two sets of observing platforms equipped with Acoustic Doppler Current Profilers (ADCP) and a suite of other sensors in the strait in January 2018. Aided by a system of high‐resolution models, we reconstructed sediment dynamics in response to the strong northerly wind of a winter storm. Model results show that the instantaneous suspended sediment flux (SSF) is highly aligned with tidal currents, while the net sediment flux has a clear dependence on variations in exchange flow and sediment resuspension. Enhanced coastal currents, intensified wave motions, and higher suspended sediment concentrations indicate that the through‐strait sediment flux during outflows is greater than during inflow conditions. Such SSF asymmetries are believed responsible for the net sediment export through the Bohai Strait in wintertime. Diagnostic analyses provided insights into the dynamic mechanisms of exchange flow variations influenced by both the strong northerly winds and the wind‐triggered coastal trapped waves in the shallow, narrow strait via geostrophic effects. This study highlights the importance of storm‐induced horizontal exchange processes in a coupled bay‐shelf system.

One-sided infections by intestinal parasites in two sympatric porpoises bycaught from the Nemuro Strait of Hokkaido, Japan.

Due to the difficulties and limitations associated with field sampling of marine mammals, quantitative surveys on their parasites are still scarce in Japan. We here report the infection statuses of intestinal parasites in harbor porpoises (n=34) and Dall's porpoises (n=10), bycaught between 2014 and 2018 by a bottom set-net fishery in the northern part of the Nemuro Strait, Japan. Necropsies of the harbor porpoises recovered one digenean, Synthesium nipponicum, and two acanthocephalans, Corynosoma sp. and Bolbosoma sp.; no infection was observed in the Dall's porpoises. The dominant parasites were Corynosoma sp. and S. nipponicum, with a prevalence of 73.53 and 64.71% and a mean abundance of 43.88 and 7.38 individuals, respectively. Although the two porpoise-species have a sympatric distribution in this narrow strait, the findings support the existence of trophic-link dependences, which can differentially affect vulnerability to these parasites.

Anopheline bionomics, insecticide resistance and transnational dispersion in the context of controlling a possible recurrence of malaria transmission in Jaffna city in northern Sri Lanka

BackgroundMalaria was eliminated from Sri Lanka in 2013. However, the influx of infected travelers and the presence of potent anopheline vectors can re-initiate transmission in Jaffna city, which is separated by a narrow strait from the malaria-endemic Indian state of Tamil Nadu.MethodsAnopheline larvae were collected from different habitats in Jaffna city and the susceptibility of emergent adults to DDT, malathion and deltamethrin investigated.ResultsAnopheline larvae were found in wells, surface-exposed drains, ponds, water puddles and water storage tanks, with many containing polluted, alkaline and brackish water. Anopheles culicifacies, An. subpictus, An. stephensi and An. varuna were identified in the collections. Adults of the four anopheline species were resistant to DDT. Anopheles subpictus and An. stephensi were resistant while An. culicifacies and An. varuna were possibly resistant to deltamethrin. Anopheles stephensi was resistant, An. subpictus possibly resistant while An. varuna and An. culicifacies were susceptible to malathion. DNA sequencing showed a L1014F (TTA to TTC) mutation in the IIS6 transmembrane segment of the voltage-gated sodium channel protein in deltamethrin-resistant An. subpictus—a mutation previously observed in India but not Sri Lanka.ConclusionAnopheles subpictus in Jaffna, like An. stephensi, may have recently originated in coastal Tamil Nadu. Besides infected overseas travelers, wind- and boat-borne carriage of Plasmodium-infected anophelines across the Palk Strait can potentially reintroduce malaria transmission to Jaffna city. Adaptation to diverse larval habitats and resistance to common insecticides in anophelines are identified as potential problems for vector control should this happen.

How long is 3km for a butterfly? Ecological constraints and functional traits explain high mitochondrial genetic diversity between Sicily and the Italian Peninsula.

Populations inhabiting Mediterranean islands often show contrasting genetic lineages, even on islands that were connected to the mainland during glacial maxima. This pattern is generated by forces acting in historical and contemporary times. Understanding these phenomena requires comparative studies integratinggenetic structure, functional traits and dispersal constraints. Using as a model the butterfly species living across the Messina strait (3 km wide)separating Sicily from the Italian Peninsula, we aimed to unravel the mechanisms limiting the dispersal of matrilines and generating genetic differentiationacross a narrow sea strait. We analysed the mitochondrial COI gene of 84 butterfly species out of 90 documented in Sicily and compared them with populations from the neighbouring southern Italian Peninsula (1,398 sequences) and from the entire Palaearctic region (8,093 sequences). For each species, we regressed 13 functional traits and 2 ecological constraints to dispersal (winds experienced at the strait and climatic suitability) against genetic differentiation between Sicily and Italian Peninsula to understand the factors limiting dispersal. More than a third of the species showed different haplogroups across the strait and most of them also represented endemic haplogroups for this island. One fifth of Sicilian populations (and 32.3% of endemic lineages) had their closest relatives in distant areas, instead of the neighbouring Italian Peninsula, which suggests high relictuality. Haplotype diversity was significantly explained by the length of the flight period, an intrinsic phenology trait, while genetic differentiation was explained by both intrinsic traits (wingspan and degree of generalism) and contemporary local constraints (winds experienced at the strait and climatic suitability). A relatively narrow sea strait can produce considerable differentiation among butterfly matrilines and this phenomenon showed a largely deterministic fingerprint. Because of unfavourable winds, populations of the less dispersive Sicilian butterflies tended to differentiate into endemic variants or to maintain relict populations. Understanding these phenomena required the integration of DNA sequences, species traits and physical constraints for a large taxon at continental scale. Future studies may reveal if the patterns here shown for mitochondrial DNA are also reflected in the nuclear genome or, alternatively, are the product of limited female dispersal.

Surface Phytoplankton Assemblages and Controlling Factors in the Strait of Malacca and Sunda Shelf

In the context of global warming and climate anomaly events, as a response, shifts in phytoplankton phenology were observed in the Strait of Malacca (SM) and Sunda Shelf (SS). Such interactions between phytoplankton structure and physico-chemical factors were less known in narrow straits. Therefore, the spatial distribution pattern and diversity of surface phytoplankton assemblage, local hydrology and nutrient regimes were investigated over the Strait of Malacca and Sunda Shelf (South China Sea, SCS) during 2017 and 2018 pre-monsoon season (spring). Diatoms, dinoflagellates and cyanobacteria were representatives of microphytoplankton in the survey area. Total phytoplankton abundance peaked near Singapore Strait (SGS) and diminished towards SS. From the lower ratio of diatoms to dinoflagellates (<3) in SS, we deduced lower carbon pump efficiency here. In agreement with the modeled results proposed previously, diatoms (especially centric form) tended to thrive in cold eutrophic water, while, dinoflagellates and filamentous cyanobacteria were much warm-adapted, they operated a feedback to cold La Nina event (negative Indian Ocean Dipole, IOD) in 2018 and warm El Nino event (positive IOD) in 2017, respectively. Specifically, diatom proportion increased by 30% and dinoflagellate, cyanobacteria reduced by 71%, 75% in response to shifts of climate anomaly from 2017 cruise to 2018 cruise. This interactive study between field microalgae and physico-chemiscal conditions would be helpful to launch large-scale climate model, biogeochemistry and carbon cycling in future research.

A modelling study of the ice-free tidal dynamics in the Canadian Arctic Archipelago

The dynamics of M2 and K1 ocean tides in the Canadian Arctic Archipelago (CAA) have been investigated using a three-dimensional hydrodynamic model, which uses an unstructured mesh with a horizontal resolution ranging from 0.5 km in narrow channels to 10–40 km in the open ocean. The model is evaluated against observed tidal elevations and tidal currents, and the evaluation indicates that the model is able to reproduce the observations at the tidal gauge sites, particularly those in the narrow straits of the CAA. In order to examine the interactions between the Arctic and the Atlantic tides in the CAA, idealized experiments were conducted by considering tidal effects through the open boundary on the Arctic and the Atlantic sides separately. The results show that the Atlantic tide is strong throughout the CAA but deceases rapidly when it encounters the open Arctic shelf for both M2 and K1 tides; on the other hand, the Arctic tide is mainly confined to the Arctic Ocean and Amundsen Gulf; it has a minor influence in the Baffin Bay. Nonlinear interactions between the Arctic and Atlantic tides are generally weak except local areas in the southern and northern CAA, where the nonlinear contribution is able to reach 10–20% of the tidal variability. Using the model results, the tidal energy flux was also analyzed, and the analysis indicated that the Lancaster Sound and Jones Sound are main pathways of the tidal energy from the Baffin Bay to the CAA, and the energy is dissipated due mainly to the vertical diffusion and the bottom friction.