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MarLIN Marine Information Network Information on the species and habitats around the coasts and sea of the British Isles Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock MarLIN – Marine Life Information Network Marine Evidence–based Sensitivity Assessment (MarESA) Review Frances Perry 2016-01-16 A report from: The Marine Life Information Network, Marine Biological Association of the United Kingdom. Please note. This MarESA report is a dated version of the online review. Please refer to the website for the most up-to-date version [https://www.marlin.ac.uk/habitats/detail/356]. All terms and the MarESA methodology are outlined on the website (https://www.marlin.ac.uk) This review can be cited as: Perry, F., 2016. Mixed fucoids, [Chorda filum] and green seaweeds on reduced salinity infralittoral rock. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. DOI https://dx.doi.org/10.17031/marlinhab.356.1 The information (TEXT ONLY) provided by the Marine Life Information Network (MarLIN) is licensed under a Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales License. Note that images and other media featured on this page are each governed by their own terms and conditions and they may or may not be available for reuse. Permissions beyond the scope of this license are available here. Based on a work at www.marlin.ac.uk (page left blank) Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock - Marine Life Information Date: 2016-01-16 Network Fucoids and Chorda filum submerged. Photographer: Sue Scott Copyright: Joint Nature Conservation Committee (JNCC) 17-09-2018 Biotope distribution data provided by EMODnet Seabed Habitats (www.emodnet-seabedhabitats.eu) Researched by Frances Perry Refereed by Admin Summary UK and Ireland classification Mixed fucoids, Chorda filum and green seaweeds on reduced EUNIS 2008 A3.341 salinity infralittoral rock Mixed fucoids, Chorda filum and green seaweeds on reduced JNCC 2015 IR.LIR.Lag.FChoG salinity infralittoral rock Mixed fucoids, Chorda filum and green seaweeds on reduced JNCC 2004 IR.LIR.Lag.FChoG salinity infralittoral rock Mixed fucoids, Chorda filum and green seaweeds on reduced 1997 Biotope IR.SIR.Lag.FChoG salinity infralittoral rock Description Permanently submerged mixed fucoids on rock in lagoons. Saccharina latissima absent, possibly due to the low salinity conditions. The main species are Fucus vesiculosus and Fucus serratus, with brown https://www.marlin.ac.uk/habitats/detail/356 3 Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock - Marine Life Information Date: 2016-01-16 Network seaweedsChorda filum, Ascophyllum nodosum, and Ectocarpaceae can be present as well. Red seaweeds are normally present and include Mastocarpus stellatus, Polyides rotunda, Chondrus crispus, Ceramium spp. and coralline crusts. A variety of green seaweeds is also present and include Ulva spp., while patches of dense Cladophora rupestris may occur on vertical rock faces. The faunal component is restricted to the mussel Mytilus edulis, the polychaete Arenicola marina and the crab Carcinus maenas. Opossum shrimps Mysidae can be present as well. (Information taken from Connor et al., 1997a, b, 2004). Depth range 0-5 m, 5-10 m Additional information Slightly deeper rock often supports Saccharina latissima (Slat.Ft), usually surrounded by more extensive areas of sediment. Often, nearby rock supports similar biotopes of submerged fucoids (AscSpAs and FcerUlv) or where salinity is further reduced ProtFur can occur. Seagrass beds thrive well in the muddy sediments of the lagoons and often cover large areas. They include both Ruppia spp. and Zostera marina and some locations in the Outer Hebrides support dense beds of the nationally rare stonewort Lamprothamnion papulosum (Rup and Zmar). The sublittoral mud, which abuts most of the submerged rock, can become anoxic and covered by a bacterial mat of Beggiatoa spp. (Beg) (Information from Connor et al., 2004). Listed By - none - Further information sources Search on: JNCC https://www.marlin.ac.uk/habitats/detail/356 4 Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock - Marine Life Information Date: 2016-01-16 Network Habitat review Ecology Ecological and functional relationships The biotope is found in very shallow submerged rocky habitats in lagoons, subject to permanently reduced salinity conditions. These particular habitat conditions lead to a variety of seaweed-dominated communities which include fucoids and green filamentous species. The fucoids, more typical of intertidal habitats, penetrate into the subtidal under the reduced salinity conditions which are not tolerated by kelps. The very sheltered conditions of the biotope enables the development of algal cover on cobbles and pebbles. In these habitats, infaunal organisms such as Arenicola marina may also be present. The fucoid species, and the other macroalgae in the biotope, increase the amount of space available for attachment, they provide shelter from wave action and can be an important food source. High abundances of algae may contribute to the oxygen budget of lagoons. Ectocarpus sp. is often found growing on other seaweeds. Grazing by littorinid snails such as Littorina littorea may be important in keeping fast growing ephemeral species such as Ulva in check. The three-spined stickleback Gasterosteus aculeatus is widely distributed throughout north-west Europe and Britain in the intertidal region, particularly in estuaries, and may be present in the SIR.FChoG biotope feeding on a wide range of invertebrates. Seasonal and longer term change The biotope occurs in extremely sheltered conditions so temporal changes associated with winter storms are not likely. However, seasonal changes in growth and recruitment are often apparent on rocky shores. Fucus serratus plants, for example, lose fronds in the winter, followed by regrowth from existing plants in late spring and summer, so that summer cover can be about 250% of the winter level (Hawkins & Hartnoll, 1980). Similar growth patterns may also occur in lagoonal habitats. Chorda filum is a summer annual, falling into decay in the autumn and disappearing during winter. Habitat structure and complexity Fucoid biotopes provide a variety of habitats and refugia for other species. The beds of Fucus serratus and Fucus vesiculosus and the presence of other algae in the biotope increases the structural complexity of the habitat providing a variety of resources that are not available on bare rock. Fronds provide space for attachment of encrusting or sessile epifauna and epiphytic algae and provide shelter from desiccation, heat and predation for invertebrates. Productivity Macroalgae rocky shore communities are highly productive and can be an important source of food and nutrients. On rocky shores only about 10% of the primary production is directly cropped by herbivores (Raffaelli & Hawkins, 1996) and this is likely to be similar for lagoonal like habitats. Macroalgae, such as Fucus serratus and other fucoids, exude considerable amounts of dissolved organic carbon which are taken up readily by bacteria and may even be taken up directly by some larger invertebrates. Dissolved organic carbon, algal fragments and microbial film organisms are https://www.marlin.ac.uk/habitats/detail/356 5 Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock - Marine Life Information Date: 2016-01-16 Network continually removed by the sea and can make a contribution to the food of many marine species through the production of planktonic larvae and propagules which contribute to pelagic food chains. However, in lagoonal like habitats such as the SIR.FChoG biotope, where tidal flows and wave exposure are weak these probably enter the food chain of local ecosystems rather than inshore subtidal or offshore ecosystems. Recruitment processes Many rocky shore species, plant and animal, possess a planktonic stage: gamete, spore or larvae which float in the plankton before settling and metamorphosing into adult form. This strategy allows species to rapidly colonize new areas that become available such as in the gaps created by storms. For these organisms it has long been evident that recruitment from the pelagic phase is important in governing the density of populations on the shore (Little & Kitching, 1996). Both the demographic structure of populations and the composition of assemblages may be profoundly affected by variation in recruitment rates. Recruitment of Fucus serratus from minute pelagic sporelings takes place from late spring until October. There is a reproductive peak in the period August - October and plants can be dispersed long distances (up to 10km). However, weak tidal streams probably results in a smaller supply of pelagic sporelings and most recruitment may come from local populations. Fucus vesiculosus gametes may be produced from mid winter until late summer with a peak of fertility in May and June. Eggs and sperm are released into the seawater and fertilised externally. Zygotes settle to the seabed and begin development wherever they fall. The egg becomes attached to the rock within a few hours of settlement and may adhere firmly enough to resist removal by the next returning tide. Visible Chorda filum sporophytes appear

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