Create long flexible habitats (>50 mm) on intertidal artificial structures

Overall effectiveness category Awaiting assessment
Number of studies: 1
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Background information and definitions

Definition: ‘Long flexible habitats’ are flexible protruding materials such as rope, ribbon or twine >50 mm in length (modified from “Soft structures” in Strain et al. 2018).

Long flexible habitats, such as macroalgal canopies and soft-bodied invertebrates, provide other organisms refuge from desiccation and temperature fluctuations during low tide in intertidal rocky habitats (Moore et al. 2007). They also provide shelter from predation (Dumas & Witman 1993). The size, density and material properties of flexible habitats are likely to affect the size, abundance and variety of organisms that can use them and the spaces they create.

Some organisms that form flexible habitats tend to be absent or sparse on intertidal artificial structures (Firth et al. 2016), although some readily colonize in wave-sheltered conditions (Jonsson et al. 2006). Artificial flexible habitats such as ropes or nets can be present on some structures, but are likely to be temporary and regularly disturbed (e.g. removed and replaced) when present. Long flexible habitats can be created on intertidal artificial structures by adding material, either during construction or retrospectively. In addition to potential biodiversity benefits, flexible habitats may offer some bioprotection for the underlying substrate, with potential to reduce weathering and enhance the durability of engineering materials (Coombes et al. 2013). Material choice is important for creating flexible habitats, since some flexible materials are unlikely to persist in the marine environment, while those that do may become entanglement hazards or contribute to pollution if dislodged. Studies that investigate the effects of transplanting live soft-bodied organisms onto structures are not included here, but are considered under the action “Transplant or seed organisms onto intertidal artificial structures”.

^{Coombes M.A., Naylor L.A., Viles H.A. & Thompson R.C. (2013) Bioprotection and disturbance: seaweed, microclimatic stability and conditions for mechanical weathering in the intertidal zone. Geomorphology, 202, 4–14.}

^{Dumas J.V. & Witman J.D. (1993) Predation by herring gulls (Larus argentatus Coues) on two rocky intertidal crab species [Carcinus maenas (L.) & Cancer irroratus Say]. Journal of Experimental Marine Biology and Ecology, 169, 89–101.}

^{Firth L.B., White F.J., Schofield M., Hanley M.E., Burrows M.T., Thompson R.C., Skov M.W., Evans A.J., Moore P.J. & Hawkins S.J. (2016) Facing the future: the importance of substratum features for ecological engineering of artificial habitats in the rocky intertidal. Marine and Freshwater Research, 67, 131–143.}

^{Jonsson P.R., Granhag L., Moschella P.S., Åberg P., Hawkins S.J. & Thompson R.C. (2006) Interactions between wave action and grazing control the distribution of intertidal macroalgae. Ecology, 87, 1169–1178.}

^{Moore P., Hawkins S.J. & Thompson R.C. (2007) Role of biological habitat amelioration in altering the relative responses of congeneric species to climate change. Marine Ecology Progress Series, 334, 11–19.}

^{Strain E.M.A., Olabarria C., Mayer-Pinto M., Cumbo V., Morris R.L., Bugnot A.B., Dafforn K.A., Heery E., Firth L.B., Brooks P.R. & Bishop M.J. (2018) Eco-engineering urban infrastructure for marine and coastal biodiversity: which interventions have the greatest ecological benefit? Journal of Applied Ecology, 55, 426–441.}

Study locations

Key messages

One study examined the effects of creating long flexible habitats on intertidal artificial structures on the biodiversity of those structures. The study was in a port in the Netherlands.

COMMUNITY RESPONSE (1 STUDY)

Overall community composition (1 study): One replicated, controlled study in the Netherlands reported that creating long flexible habitats on intertidal artificial structures altered the combined macroalgae and non-mobile invertebrate community composition on structure surfaces. The flexible habitats themselves supported macroalgae, mobile and non-mobile invertebrates that were absent from structure surfaces without flexible habitats.

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

One replicated, controlled study in 2009 on five intertidal jetty pilings in the Port of Rotterdam, the Netherlands (Paalvast et al. 2012) reported that creating long flexible habitats (‘hulas’) on pilings altered the macroalgae and non-mobile invertebrate community composition on piling surfaces, and that hulas were colonized by macroalgae and invertebrates, but data were not statistically tested. After eight months, hula ropes supported mussels (Mytilus edulis: 5% cover), barnacles (Amphibalanus improvisus: 1%), red macroalgae (Ceramium rubrum: 0.2%) and amphipods (Amphipoda: 11–100 individuals/rope), which were all absent from piling surfaces without flexible habitats. Average biomass on ropes was 1 g/cm. Piling surfaces under hulas supported mostly barnacles (50% cover), while pilings without flexible habitats supported mostly green macroalgae (50% cover). Long flexible habitats were created by attaching polyamide rope skirts (‘hulas’) around pilings in March 2009. One hula with 167 ropes (diameter: 6 mm; length: 550 mm; density: 167/m) was attached at lowshore around each of five wooden pilings, cleared of organisms. Hulas were compared with intertidal surfaces (200 × 200 mm) on five pilings without flexible habitats, cleared of organisms. Macroalgae and invertebrates on hula ropes and piling surfaces were counted and biomass (wet weight) measured in the laboratory over eight months.
Study and other actions tested
Referenced paper
Paalvast P., van Wesenbeeck B.K., van der Velde G. & de Vries M.B. (2012) Pole and pontoon hulas: an effective way of ecological engineering to increase productivity and biodiversity in the hard-substrate environment of the port of Rotterdam. Ecological Engineering, 44, 199-209.

Please cite as:

Evans, A.J., Moore, P.J., Firth, L.B., Smith, R.K., and Sutherland, W.J. (2021) Enhancing the Biodiversity of Marine Artificial Structures: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Biodiversity of Marine Artificial Structures

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