Effects of Dredging Activities on Growth of Laminaria saccharina

Abstract

Abstract. The possible effects of fine‐grained deposits on the photosynthesis, growth, and nutrient uptake of Laminaria have been studied in field and laboratory experiments. Some of the plants were treated with fine‐grained material for two hours and then transplanted in rows together with untreated plants. At two‐week intervals the treatment was repeated and samples collected. The macroalgae were analyzed for growth as well as chlorophyll a, nitrogen, and phosphorus content. In the laboratory experiments, plants of a uniform size were incubated in Plexiglas containers after leaf‐marking and treatment in a sediment suspension. At weekly intervals, photosynthesis, growth, chlorophyll a, and nutrients were analyzed. The field study showed that Laminaria growth was significantly affected by the fine‐grained material. The growth in the control experiment was 20% higher than in the treated plants. The chlorophyll a concentrations in the treated plants were significantly lower than in the control experiment, and the results indicated a reduced nutrient uptake in the treated plants. In the laboratory experiments the growth of the treated plants was only 30% of the controls, but no differences in photosynthetic capacities were detected. Nitrogen uptake was reduced in the treated plants, but no effects were observed on phosphorus uptake. Thick layers of fine‐grained material caused direct harmful effects and rotting. The results are discussed in relation to dredging activities; it is concluded that in heavy sedimentation areas, Laminaria growth may be significantly reduced beyond the indirect effect of shading from suspended material in the water.

Storm-generated sediment deposition on rocky shores: Simulating burial effects on the physiology and morphology ofSaccharina latissimasporophytes

“…The effects of sediments on kelps ranged from a reduction in photosynthesis, to bleaching and tissue decay. The same effects of sediments from dredging activities were observed on photosynthesis, growth, pigment and nutrient uptake of Saccharina latissima (previously Laminaria saccharina, Lyngby & Mortensen 1996). Under sediment burial, adverse light and anaerobic conditions did not affect survival of Fucus embryos, but the presence of hydrogen sulphide had overriding negative impacts (Chapman & Fletcher 2002).…”

“…Few studies have looked into the basic physiological responses, such as photosynthesis, growth, and pigments at the organism level (e.g. Lyngby & Mortensen 1996;Roleda et al 2008).…”

An investigation of the relationship between sediment particles size and the development of green algal mats (Ulva prolifera) on the intertidal flats of Muan, Korea

“…On rocky shore habitats, it has been demonstrated for a range of algal species that sediment deposition can interfere with the attachment of microscopic stages of seaweeds (Norton 1978;Littler et al 1983;Arakawa and Matsuike 1992). In addition to impairing the initial attachment process, burial under sediment may significantly reduce growth and impair the regeneration ability of adults (Lyngby and Mortensen 1996). Scour through sediment movement removes small life stages of macroalgae from the substratum and hence reduces successful recruitment (Devinny and Volse 1978).…”

Seasonal Patterns of Sporophyte Growth, Fertility, Fouling, and Mortality ofSaccharina latissimain Skagerrak, Norway: Implications for Forest Recovery

“…All monitored kelp individuals were transplanted from areas with healthy S. latissima forests, which were only found on moderately exposed sites. Transplantation is a widely used methodology in studies of kelp biology (see e.g., [14][15][16][17][18][19] • C each year were extracted for analytic purposes, as the summer isotherm of 19-21…”