Biogeography of Wood-Boring Crustaceans (Isopoda: Limnoriidae) Established in European Coastal Waters

Marine wood-borers of the Limnoriidae cause great destruction to wooden structures exposed in the marine environment. In this study we collated occurrence data obtained from field surveys, spanning over a period of 10 years, and from an extensive literature review. We aimed to determine which wood-boring limnoriid species are established in European coastal waters; to map their past and recent distribution in Europe in order to infer species range extension or contraction; to determine species environmental requirements using climatic envelopes. Of the six species of wood-boring Limnoria previously reported occurring in Europe, only Limnoria lignorum, L. quadripunctata and L. tripunctata are established in European coastal waters. L. carinata and L. tuberculata have uncertain established status, whereas L. borealis is not established in European waters. The species with the widest distribution in Europe is Limnoria lignorum, which is also the most tolerant species to a range of salinities. L. quadripunctata and L. tripunctata appear to be stenohaline. However, the present study shows that both L. quadripunctata and L. tripunctata are more widespread in Europe than previous reports suggested. Both species have been found occurring in Europe since they were described, and their increased distribution is probably the results of a range expansion. On the other hand L. lignorum appears to be retreating poleward with ocean warming. In certain areas (e.g. southern England, and southern Portugal), limnoriids appear to be very abundant and their activity is rivalling that of teredinids. Therefore, it is important to monitor the distribution and destructive activity of these organisms in Europe

Diversity, environmental requirements, and biogeography of bivalve wood-borers (Teredinidae) in European coastal waters

Background: Bivalve teredinids inflict great destruction to wooden maritime structures. Yet no comprehensive study was ever carried out on these organisms in European coastal waters. Thus, the aims of this study were to: investigate the diversity of teredinids in European coastal waters; map their past and recent distributions to detect range expansion or contraction; determine salinity-temperature (S-T) requirements of species; flag, for future monitoring, the species that pose the greatest hazard for wooden structures. Results: A total of nine teredinid species were found established in European coastal waters. Seven were considered cryptogenic, of unknown origin, and two were considered alien species. Teredo navalis and Nototeredo norvagica were the species with the widest distribution in European waters. Recently, T. navalis has been reported occurring further east in the Baltic Sea but it was not found at a number of sites on the Atlantic coast of southern Europe. The Atlantic lineage of Lyrodus pedicellatus was the dominant teredinid in the southern Atlantic coast of Europe. In the Mediterranean six teredinid species occurred in sympatry, whereas only three of these occurred in the Black Sea. The species that pose the greatest hazard to wooden maritime structures in European coastal areas are T. navalis and the two lineages of L. pedicellatus. Conclusions: Combined data from field surveys and from the literature made it possible to determine the diversity of established teredinid species and their past and recent distribution in Europe. The environmental requirements of species, determined using climatic envelopes, produced valuable information that assisted on the explanation of species distribution. In addition, the observed trends of species range extension or contraction in Teredo navalis and in the two lineages of Lyrodus pedicellatus seem to emphasise the importance of temperature and salinity as determinants of the distribution of teredinids, whereas their life history strategy seems to play an important role on competition. Teredo navalis and pedicellatus-like Lyrodus species should be monitored due to their destructive capability. The two alien species may expand further their distribution range in Europe, becoming invasive, and should also be monitored.This research was partially funded by Fundação para a Ciência e a Tecnologia, Portugal through a personal grant to LB (SFRH/BD/17915/2004)

The Role of Turbulence in Fueling the Subsurface Chlorophyll Maximum in Tidally Dominated Shelf Seas

Glider observations show a subsurface chlorophyll maximum (SCM) at the base of the seasonal pycnocline in the North Sea during stable summer conditions. A colocated peak in the dissipation rate of turbulent kinetic energy suggests the presence of active turbulence that potentially generates a nutrient flux to fuel the SCM. A one‐dimensional turbulence closure model is used to investigate the dynamics behind this local maximum in turbulent dissipation at the base of the pycnocline (PCB) as well as its associated nutrient fluxes. Based on a number of increasingly idealized forcing setups of the model, we are able to draw the following conclusions: (a) only turbulence generated inside the stratified PCB is able to entrain a tracer (e.g., nutrients) from the bottom mixed layer into the SCM region; (b) surface wind forcing only plays a secondary role during stable summer conditions; (c) interfacial shear from the tide accounts for the majority of turbulence production at the PCB; (d) in stable summer conditions, the strength of the turbulent diapycnal fluxes at the PCB is set by the strength of the anticyclonic component of the tidal currents.Plain Language Summary: Many midlatitude shelf seas are vertically stratified in summer, where a warm surface layer sits on top of a cold, dense bottom layer. Both of these layers are unproductive environments for phytoplankton—the bottom layer is light limited, and the surface layer is nutrient‐limited. However, abundant phytoplankton is observed directly at the interface between surface and bottom layers. In order to sustain this phytoplankton, nutrient‐rich bottom water needs to be mixed with interface water. While both wind and tides are major causes for mixing in the coastal ocean, we find that the tides alone provide sufficient stirring at the right place to potentially act as an effective fuel pump for the phytoplankton. Interestingly, it is not the strength of the tides alone that counts, rather the sense of rotation of the tidal currents; rotation opposite to the Earth's spin causes more stirring than rotation along with it.Key Points: Turbulence and chlorophyll both peak at the base of the pycnocline on a mid‐latitude shelf. Locally generated turbulence at the pycnocline base is a fuel pump for the subsurface chlorophyll maximum. Amplitude and polarity of the M2 tide govern the local generation of turbulence at the pycnocline base.Helmholtz Associationhttps://doi.org/10.5281/zenodo.3525787https://oceancolor.gsfc.nasa.gov/l3/https://www.cen.uni-hamburg.de/icdc/data/ocean/nsbc.htm

Storm-induced turbulence alters shelf sea vertical fluxes

Storms are infrequent, intense, physical forcing events that represent a potentially significant driver of ocean ecosystems. The objective of this study was to assess changes in water column structure and turbulent fluxes caused by storms using an autonomous underwater glider, as well as the chlorophyll a (Chl a) response to the altered physical environment. The glider was able to measure throughout the complete life cycle of Storm Bertha as it passed over the North Sea in August 2014, from its arrival to dissipation. Storm Bertha triggered rapid mixing of the thermocline through shear instability, increasing vertical fluxes by nearly an order of magnitude, and promoting increases in surface layer Chl a. The results demonstrate that storms represent a significant fraction of seasonal vertical turbulent fluxes, with potentially important consequences for biological production in shelf seas

Sites surveyed between 2001 and 2011.

<p>Sites surveyed between 2001 and 2011.</p

Location of test sites.

<p>Site name; geographic coordinates (decimal degrees); time and duration of surveys; and type of structure from which limnoriids where collected from.</p><p>Location of test sites.</p

Distribution of the three limnoriid species in salinity-temperature (<i>S–T</i>) space.

<p>The minimum convex polygon encompassing all data points represent the climatic niche of each species.</p

Past and present distribution of <i>Limnoria lignorum</i>, <i>L. quadripunctata</i> and <i>L. tripunctata</i> in European coastal waters.

<p>Squares represent data obtained from the literature before 2000; black circles represent data obtained from field surveys between 2001 and 2011; white circles represent data reported in the literature since 2000.</p

Specimens of <i>Limnoria lignorum</i>, <i>L. quadripunctata</i> and <i>L. tripunctata</i> collected in the field surveys.

<p>A) Dorsal view of preserved specimen of <i>L. lignorum</i>; B) dorsal view of preserved specimen of <i>L. quadripunctata</i>; C) dorsal view of preserved specimen of <i>L. tripunctata</i>; D) ventral view of preserved specimen of <i>L. tripunctata</i>. Scale bar = 0.5 mm.</p

Shear Instability and Turbulence Within a Submesoscale Front Following a Storm

Narrow baroclinic fronts are observed in the surface mixed layer (SML) of the Baltic Sea following an autumn storm. The fronts are subjected to hydrodynamic instabilities that lead to submesoscale and turbulent motions while restratifying the SML. We describe observations from an ocean glider that combines currents, stratification, and turbulence microstructure in a high horizontal resolution (150–300 m) to analyze such fronts. The observations show that SML turbulence is strongly modulated by frontal activity, acting as both source and sink for turbulent kinetic energy. In particular, a direct route to turbulent dissipation within the front is linked to shear instability caused by elevated nongeostrophic shear. The turbulent dissipation of frontal kinetic energy is large enough that it could be a significant influence in the evolution of the front and demonstrates that small‐scale turbulence can act as a significant sink of submesoscale kinetic energy.Key Points: An autonomous ocean glider observed turbulence, currents, and stratification in surface mixed layer submesoscale fronts following a storm. Submesoscale fronts provide both a damping and generation of surface mixed layer turbulence. Shear instability within the front could represent a significant energy transfer in frontal evolution.Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659Helmholtz Association http://dx.doi.org/10.13039/50110000165