Ficopomatus enigmaticus Fauvel 1923

Reefs provide habitat and beneficial conditions for invasives Monocorophium insidiosum and Tubificoides brownae (Heiman, et al., 2008).

The calcareous serpulid worm Ficopomatus enigmaticus (Fauvel) is prominent in the coastal lagoon of the Albufera of Menorca, where it encrusts \"hard substrates\". Its bioconstructions differ in shape depending on location, substratum and water level. This worm occurs along the entire littoral area, forming a continuous layer up to 3 m thick. On the bottom of the lagoon, they develop as micro-atolls (in the shallowest areas) and patch reefs (over 2 m height and 4 m in diameter) encrusting molluscan shells, boulders and small rock outcroppings. Although the worm needs a hard substratum for fixation, growth over molluscan shells can result in a spread-out worm reef overlying a muddy substrate. Fluctuations in water level causes death of the emergent parts of the reef, although these are easily recolonized when the environmental conditions change. The best physico-chemical conditions for the development of Ficopomatus on these islands seem to be in the Albufera of Menorca, where it attains an annual production in dry weight of 21.269 kg m-2 yr-1. The environmental conditions present are 9.6-27.2°C temperature, 9.5-30.0%0 salinity, 1.75-3.75 meq 1-1 alkalinity and 36-202% oxygen saturation, of annual oscillation. The rapid and spectacular growth of these bioconstructions that occurs in the coastal lagoon can cause change in the ecological dynamics. The lagoon can be progressively filled up by reefs and skeletal debris of serpulids and associated benthic organisms. (Fornós et al. 1997)

Experimental results suggests that Ficopomatus reefs are able to strongly alter the physical characteristics in the invaded environment (Schwindt et al., 2001). Only juvenile nereids, ostracodes, nematodes, harpacticoid copepods, and the gastropod Heleobia conexa are typical brackish organisms found in the lagoon throughout the year (Schwindt, 2001a). The most abundant organisms in the traps were ostracodes and nematodes, showing lower densities near the reefs during a different day observed for the sediment transported. This difference in days may come from the highest wind speed (up to 30 km h
1) observed during the day when nematodes and ostracodes showed a significant transport. This evidence suggests that both the direction and intensity of the wind are important variables for the transport of sediment and organisms. ... Even though total bedload organism transport is not related to wind speed, reefs affected the transport of the organisms (i.e. nematodes and ostracodes) and this may be an evidence for how changes in depositional and transport processes can affect the local distribution of organisms (Cusson and Bourget, 1997). After the link between an organism’s activities and the ecosystem emerged under the concept of ecosystem engineering (Jones et al., 1994, 1997), the role of species in structuring ecosystems was recognized in terrestrial (e.g. Reichman and Seabloom, 2002) and aquatic (e.g. Coleman and Williams, 2002) systems. This concept is especially interesting when the ecosystem engineers studied are invasive species (e.g. Crooks and Khim, 1999; Reusch and Williams, 1998; Posey, 1988) because their impact may be magnified at large spatial scale while spreading. The exotic ecosystem engineer Ficopomatus enigmaticus builds reefs that are known to create refuge for other organisms such as amphipods, crabs and gastropods (Schwindt et al., 2001). In this work we show that F. enigmaticus also physically modified the estuarine ecosystem where it was introduced by altering sediment dynamics. In so doing, reefs favor the sediment deposition around them and may generate resources (e.g. refuge) for several native soft-bottom organisms. Considering that 86% of the estuarine environment is already populated by reefs (Schwindt et al., 2001), and they are increasing over time, they may completely alter the entire environment in the long term. Our results agree with the hypothesis that this exotic ecosystem engineer is favoring the filling in of the estuarine environment and may eventually change the landscape in the long term (Isla and Gaido, 2001). (Schwindt et al. 2004)