Artificial structures in sediment-dominated estuaries and their possible influences on the ecosystem

Abstract

a b s t r a c tArtificial substrates are omnipresent today in most estuaries mostly in form of massive rip-rap used for groynes and jetties. In the Weser estuary, Germany, 60% of the shoreline is covered with such artificial substrates while, natural rocky substrate is lacking, as in all Wadden Sea estuaries. This large quantity of artificial substrates may be colonized by a benthic hard-substrate community which differs from the local natural soft-substrate assemblage. In this study we examined species compositions, abundances, biomass, and numbers of species of subtidal benthic communities on groynes and in the natural habitat, the sediment, along the salinity gradient of the Weser estuary. Species composition changed on both substrates significantly with salinity and was also significantly different between the substrates. In a comparison with the sediment, the groynes did not provide any benefit for non-indigenous nor for endangered species in terms of abundance, biomass, and number of species, but represent habitats with higher total abundances and biomass; though some non-indigenous species even occurred exclusively on groynes. In particular, groynes supported filter-feeding organisms which play an important role by linking benthic and pelagic food webs. The dominance of the suspension feeders affects crucial estuarine ecosystem services and may have important implications for the estuarine management by altering the estuarine ecological quality status. Hence, artificial substrates should be considered in future conservation planning and in ecological quality monitoring of the benthic fauna according to the European Water Framework Directive.

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats

“…A recent study also found that H. capensis were more likely to move towards or remain on a Reno mattress structure compared to Z. capensis (Claassens et al ., ), which suggests that this habitat type has some positive feature (food, holdfasts, protection) preferred by H. capensis . Artificial structures have the potential to provide much needed habitat to threatened aquatic species (Guerra‐Garcia et al ., ; Perkol‐Finkel et al ., ; Wetzel et al ., ), but this does not necessarily equate to an overall benefit for the system (or even the species in question), particularly if these artificial habitats displace natural aquatic habitats (Waltham & Connolly, ; Wetzel et al ., ). The Reno mattresses in Thesen Islands Marina did not displace any natural aquatic habitat and thus provide a net increase in habitable environments for H. capensis in the Knysna Estuary.…”

Human impact on large rivers: the influence of groynes of the River Oder on larval assemblages of caddisflies (Trichoptera)

“…In the Oder, we found filter feeder-predators to be the most numerous at the currents sites, while shredder-predators were the most numerous at the control sites and in the groyne fields. The presence of numerous filter feeders may be beneficial as regards improving water quality in a river such as the Oder: this was noted by Wetzel et al (2014), who studied estuarine ecosystems with groynes in Germany. Among all riverine habitats, the trophic structure of the groyne fields was the most diversified and similar to the structure of the oxbows.…”

Comparação de substratos artificiais na redução de bioincrustantes em um cultivo de ostras no estuário amazônico

“…Em consequência da importância ecológica da comunidade bentônica, diversas linhas de pesquisas se desenvolvem desde a década de 1970 (Fernandes et al, 2010). Dentre os estudos realizados, destacam-se aqueles que descrevem a dinâmica espaço-temporal no processo de colonização e a estrutura da comunidade em ambientes naturais e artificiais (Carvalho & Uieda, 2004, Nery et al, 2008, Souza et al, 2008, Fernandes et al, 2010, Pereira et al, 2010, Braga et al, 2013, Guerra-Castro & Cruz-Motta, 2014, Wetzel et al, 2014, Bernardino et al, 2015, Oliveira & Manso, 2016, Chagas et al, 2018.…”