Teredo navalis in the Baltic Sea: Larval Dynamics of an Invasive Wood-Boring Bivalve at the Edge of Its Distribution

Abstract

Wooden groin systems on the southwestern Baltic Sea coast are a traditional and important coastal-protection facility, but have been regularly infested and destroyed by the wood-boring bivalve Teredo navalis since the early 1990s. The occurrence of T. navalis was presumed to be limited mainly by the prevailing low salinities. Recently, a possible range expansion of this invasive species to the more eastern parts of the Baltic Sea has been discussed. T. navalis larval settlement was therefore monitored at the distribution boundary of the species in the Baltic Sea over a period of 4 years. At 7 stations along the prevailing salinity gradient on the Mecklenburg-western Pomeranian coast, larval traps were installed at regular time intervals, while at the same time water temperature and salinity were measured continuously every hour. Correlations between measured abiotic parameters and borehole abundance of T. navalis were tested. For the German Baltic Sea coast, no range expansion of T. navalis was confirmed. The salinity and temperatures at the groin systems varied among the study years, and significant correlations between T. navalis borehole abundance and salinity as well as temperature were found. Higher summer temperatures favor the T. navalis borehole abundance on the Mecklenburg-western Pomeranian coast, and may slightly shift the distribution border of this species toward lower salinities.

Durability and protection of timber structures in marine environments in Europe: An overview

“…However, high variation in abundance also depending on the evaluation year, made it difficult to explain the factors controlling the settlement. The distribution of this shipworm species could be slightly changed towards the Mecklenburg-Western Pomeranian Baltic Sea coast, where a dramatic increase in the amount of damage in timber structures was observed (Lippert et al 2017).…”

“…While no evidence of the invasion of the Baltic Sea by teredinid recruits was found on the Swedish coast (Appelqvist et al 2014), it is reported that shipworm is spreading within the Southern part of the Baltic Sea, leading to severe problems and economic damages in Denmark, Germany, Poland, and Southern Sweden (Sordyl et al 1998;Borges et al 2014b;Lippert et al 2017). While the abundance of Teredo navalis was positively correlated to the surface water salinity, no positive correlation to temperature could be shown.…”

A comparison of biodegradation caused by Teredinidae (Mollusca:Bivalvia), Limnoriidae (Crustacea:Isopoda), and C. terebans (Crustacea:Amphipoda) across 4 shipwreck sites in the English Channel

“…Whilst Limnoria and C.terebans preferred pine test panels, results indicated Teredinidae were less selective and no relationships were observed between the total number of boreholes or successful boreholes in relation to wood type (Table 5). This is likely due to their life history strategies; Teredinidae are opportunistic with a limited window to locate a suitable substrate in their larval form (Appelqvist et al 2015, Lippert et al 2017, thus they cannot be overly selective and using chemical cues to determine a suitable location near conspecifics with available space is likely prioritised (Toth et al 2015); this behaviour may explain results seen on Poole Cannon Site where a higher number of total boreholes were identified on elm test panels (Table 4). On the other hand, Limnoria and C.terebans are born into a protective environment and have the ability to migrate in search of substrate material and, move at will when conditions become unfavourable (Mohr 1959, Cragg et al 1999, Poore et al 2002, Thiel 2003, Green Etxabe 2013; this is evident on the London where borings were present but no abundance of Limnoria was found, thus Limnoria likely migrated when sediment coverage occurred.…”

“…Both are protandrous hermaphrodites; born as males, they later transition into females, and spawn free swimming larvae into the water column (Coe 1943, Lane 1959, Appelqvist & Havenhand 2016. T.navalis remains in the water column for 17-34 days before settlement, and are capable of travelling large distances and inhabiting a range of sites (Appelqvist et al 2015, Lippert et al 2017. L.pedicellatus retains their eggs until they are further along in their developmental stage (Wurzinger-Mayer et al 2014); due to this, L.pedicellatus remain in the water column for 24-48 hours, making them more likely to recolonise the same site compared to T.navalis (Borges et al 2010).…”

“…This method aids in minimising larval mortality and the risk of being carried to unfavourable environments. After settlement, Teredinidae larvae metamorphose, and the development of a shell covered in serrated teeth enables them to bore, and tunnel formation begins (Quayle 1992, Lippert et al 2017. Within these tunnels, Teredinidae grow and consume wood for the duration of their lives, however, survival and growth of Teredinidae is linked to the availability of wood, thus rapid settlement and growth are vital to survival (Cragg et al 2009, Macintosh et al 2014 but detrimental to the wood they live within.…”