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

Published source details 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.
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This study is summarised as evidence for the following.

	Action	Category
	Create long flexible habitats (>50 mm) on intertidal artificial structures Action Link
	Create long flexible habitats (>50 mm) on subtidal artificial structures Action Link
	Create long flexible habitats (>50 mm) on subtidal artificial structures Action Link

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

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.

(Summarised by: Ally Evans)
Create long flexible habitats (>50 mm) on subtidal artificial structures

One replicated, controlled study in 2009 on seven subtidal jetty pilings in the Port of Rotterdam, the Netherlands (Paalvast et al. 2012a) reported that creating long flexible habitats (‘hulas’) on pilings altered the non-mobile invertebrate community composition and reduced mussel Mytilus edulis cover on piling surfaces, but that hulas supported higher macroalgae and invertebrate biomass (mostly mussels) than piling surfaces without flexible habitats. Data were not statistically tested unless stated. After eight months, hula ropes supported mussels (60% cover), nine macroalgae and other non-mobile invertebrate species (0–2% cover), and five mobile invertebrate species groups (1–10 to >100 individuals/rope). Piling surfaces under hulas had 50% barnacle cover (Amphibalanus improvisus), while pilings without flexible habitats had 50% mussel and 14% barnacle cover. At least eight species (2 macroalgae, 6 non-mobile invertebrates) recorded on hulas were absent from piling surfaces without. Biomass was 44–113 kg/m² on hulas and 10 kg/m² on surfaces without. Biomass was statistically similar on ropes at 0.5 m depth (6 g/cm) and 1 m (7 g/cm), and higher on both than those at 0 m (3 g/cm). Long flexible habitats were created by attaching nylon rope skirts (‘hulas’) around pilings in March 2009. Three overlapping hulas with 167 ropes/hula (rope diameter: 6 mm; length: 550 mm; density: 167/m) were attached around each of five wooden and two steel pilings, cleared of organisms, with one hula at each of 0, 0.5 and 1 m depths. Hulas were compared with subtidal surfaces (200 × 200 mm) on seven additional wooden/steel pilings without hulas, 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.

(Summarised by: Ally Evans)
Create long flexible habitats (>50 mm) on subtidal artificial structures

One replicated study in 2009 on five subtidal pontoons in the Port of Rotterdam, the Netherlands (Paalvast et al. 2012b) found that long flexible habitats (‘hulas’) created under pontoons supported different invertebrate biomass depending on the rope length and density. After eight months, around hula edges, biomass of mussels Mytilus edulis, and other mobile and non-mobile invertebrates was higher on hulas with long ropes (17–19 g/cm) than mixed-length ropes (14–16 g/cm). In hula centres, biomass was similar on both designs (long ropes: 9–13 g/cm; mixed: 10–15 g/cm). Biomass was higher on hulas with low-density ropes (15 g/cm) than medium-density (12 g/cm), and higher on both than those with high-density (9 g/cm). Long flexible habitats were created by suspending plastic frames with nylon rope skirts (‘hulas’, 12 mm rope diameter) beneath five pontoons in March 2009. Two hulas (2.0 × 1.6 m, 208 ropes/hula) had different rope lengths (long: 1.5 m; mixed: 0.3–1.5 m), while three hulas (2.3 × 0.9 m, 1.5 m rope length) had different rope densities (high: 64 ropes/m²; medium: 32/m²; low: 16/m²). Invertebrates on hula ropes were counted and biomass (wet weight) measured in the laboratory over eight months.

(Summarised by: Ally Evans)