The Role of Kelp in the Marine Environment - National Parks ...

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Methods of Kelp Harvesting Impact Review In France, to effectively harvest large amounts of Laminaria digitata, a mechanical kelp harvester was developed called “Scoubidou”. This piece of machinery is operated from an 8–12 meter long boat manned by one or two harvesters. The larger boats can carry two Scoubidou's. The Scoubidou twists and wraps around the kelp after which it is pulled out by an hydraulic arm; it can pull up about 10 kg of L. digitata per extraction, which takes about 30 seconds. Laminaria hyperborea harvesting is a well-established industry in Norway. FMC BioPolymer AS harvests yearly 140,000–180,000 tonnes of L. hyperborea for the alginate industry. It is harvested by specially designed seaweed trawlers that use a dredge developed by the company. The 15 boats that operate along the Norwegian coast today can carry between 30 and 150 tonnes each. The harvesting dredge has worked well in Norway; however, if the coastline is too rocky the harvesting machinery cannot be deployed. Production Repeated cutting of kelp forest is experienced by the plants as a type of environmental disturbance or pressure. Different harvesting regimes will have different effects on both the target species and the containing ecosystem. For this reason we discuss in some detail the most likely harvesting methods and their associated impacts, under the following headings: The impact of harvesting on species composition of kelp beds Hawkins and Harkin (1985) and Smith (1985) have studied the effects of removing the algal canopy in kelp beds. Hawkins and Harkin (op. cit.) simultaneously removed Laminaria digitata and L. hyperborea at sites in the Isle of Man where they coexisted; subsequently L. digitata exclusively re-occupied the substratum. Thus, the exploitation of mixed areas may promote a relative increase in L. digitata beds at the expense of L. hyperborea. In 1997, the productivity of L. digitata began to decrease on many sites in Brittany while Sacchoriza polyschides was recorded in greater 47
numbers at the same sites (Arzel, 2000). As competition between L. digitata and S. polyschides is known to occur, the question to be answered is whether L. digitata is in decline, thus offering more space for Sacchoriza colonization or whether L. digitata is being actively displaced by S. polyschides competition. Several explanations are under investigation (Arzel, 2000): � the exploitation method : successive modification of the harvesting tool have resulted in more stipes being left on the substrate than previously. � the Sacchoriza life cycle is shorter than that of L. digitata, thus favouring the former, on a substratum already open to recruitment by intensive cutting, much as L. digitata displaced L. hyperborea in the case already discussed. � 10% of the boulders are turned upside down during harvesting, resulting in fast colonization of the blank face by opportunistic fast-growing Chlorophyceae, then by S. polyschides. � the abrasive effect of sand is an indirect effect of substrate loss. Abrasion is lethal to Laminariales gametophytes and young sporophytes. � climatic events: the frequency of major storms has increased over the last decade with direct effect on kelp beds : plants are torn away and more sand abrasion occurs. � water temperature : an increase in temperature has been documented in Brittany which is at the southern limit for L. digitata. The upper temperature for L. digitata is 20°C and in Brittany this can be reached in summer. Sacchoriza is more temperature tolerant and is distributed down to northwest coasts of Africa. � photo-inhibition from U.V radiation is often lethal to sporophytes and especially on gametophytes. This factor may harm L. digitata during summer especially on the younger individuals after harvesting of most of the protective canopy. � pollution. It is clear that unforeseen changes in species composition are associated with intensive harvesting of the kelp resource. There appears to be a tendency for short lived species to replace long lived species. This tendency must result in the reduction of populations of L. hyperborea, when intensively harvested. 48
Page 1: The Role of Kelp in the Marine Envi
Page 4 and 5: Details of Contributors Birds Fish
Page 6 and 7: Executive Summary Kelp forests have
Page 8 and 9: Birds Acknowledgements Professor R.
Page 10 and 11: Introduction Kelp species represent
Page 12 and 13: Each year the kelp plant renews its
Page 14 and 15: estimate (Birkett et al., 1998) of
Page 16 and 17: Other researchers have highlighted
Page 18 and 19: Figure 2 δ 13 C values from the di
Page 20 and 21: kelp population was estimated by Ar
Page 22 and 23: Figure 4 Growth in length of the la
Page 24 and 25: varies with the age of the plants.
Page 26 and 27: Table 3 Primary production as tonne
Page 28 and 29: accuracy. Most epiphytic algae are
Page 30 and 31: collected off the Cumbrian coast ri
Page 32 and 33: Lavery et al. (1999) and Dugan et a
Page 34 and 35: (op. cit.) and Lorentsen et al. (op
Page 36 and 37: Laridae (Gulls) e.g., Herring Gull
Page 38 and 39: Interesting studies of the interact
Page 40 and 41: 1985). These birds prey upon e.g. b
Page 42 and 43: as amphipods and crabs beneath. Pur
Page 44 and 45: An interesting and indirect interac
Page 46 and 47: 5-8% lower than velocities above th
Page 50 and 51: Scale of kelp removal It is self ev
Page 52 and 53: Blade cutting vs. complete plant re
Page 54 and 55: � fallow years, as successfully p
Page 56 and 57: trophic and habitat associations (N
Page 58 and 59: Foreman (1984) noted that if sustai
Page 60 and 61: variability in benthic community st
Page 62 and 63: lock was occupied by laminarians an
Page 64 and 65: Laminaria hyperborea (Gunn.) Foslie
Page 66 and 67: Pylophora crispa, 1% Ceramium nodul
Page 68 and 69: Most species on L. digitata were en
Page 70 and 71: after 3 days exposure in September
Page 72 and 73: many species have planktonic larvae
Page 74 and 75: decline in juvenile rockfishe, i.e.
Page 76 and 77: Species classified as threatened or
Page 78 and 79: The conservation status of bird spe
Page 80 and 81: Production Future Research Nearly a
Page 82 and 83: � Biomass and standing stock surv
Page 84 and 85: legislative obligations in relation
Page 86 and 87: Conclusions Even well managed kelp
Page 88 and 89: waters and with the postulated rise
Page 90 and 91: Arzel, P. (1998). Les laminaires su
Page 92 and 93: Bustamante, R. H. & Branch, G. M. (
Page 94 and 95: Christie, H., Jorgensen, N.M., Nord
Page 96 and 97: Deady, S. and Fives, J.M. (1995b).
Page 98 and 99:
ecosystems. Bulletin of Marine Scie
Page 100 and 101:
Graham, M. H. (2002). Prolonged rep
Page 102 and 103:
Kain, J. M. (1977). The Biology of
Page 104 and 105:
Mann, K. H. (1988). Production and
Page 106 and 107:
Nicholson, N.L. (1970). Field studi
Page 108 and 109:
Quast, J. C. (1968a). Fish fauna of
Page 110 and 111:
Sellers, R. M. (2004). The Great Co
Page 112 and 113:
Swaby, S.E. and Potts, G.W. (1990).
Page 114 and 115:
Went, A. E. J. (1957). List of Iris
Page 116 and 117:
Appendix 2 Macroinvertebrate specie
Page 118 and 119:
Gibbula umbilicalis Helcion pelluci
Page 120 and 121:
Appendix 3 Description of habitat,
Page 122 and 123:
Appendix 3 continued Anguilla angui
Page 124:
Appendix 4 Conservation status of b
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