ABSTRACT

Macroal​gal mass blooms and ac​cu​mu​lat​ing beach-cast are in​creas​ing prob​lems in many coastal ar​eas. How​ever, beach-cast is also a po​ten​tially valu​able ma​rine biore​source, e.g. as a biofer​tiliser in coastal agri​cul​ture. One lim​it​ing fac​tor in use of beach-castas a fer​tiliser is un​cer​tainty re​gard​ing the cad​mium (Cd) con​cen​tra​tion de​pend​ing on beach-cast com​po​si​tion and lo​ca​tion.

In this study, chem​i​cal analy​ses were per​formed on beach-cast from Burgsviken Bay in the island of Got​land, in the Baltic Sea. The re​sults re​vealed large vari​ations in cad​mium con​cen​tra​tion de​pend​ing on sam​pling lo​ca​tion and beach-cast com​po​si​tion, with lev​els rang​ing be​tween 0.13 and 2.2​mg Cd/​kg dry mat​ter (DM). Of 15 beach-cast sam​ples analysed, one had a cad​mium con​tent above the Swedish statu​tory limit for biofer​tiliser (2​mg Cd/​kg DM) and four had val​ues above the limit sug​gested by the Swedish En​vi​ron​men​tal Pro​tec​tion Agency for 2030 (0.8​mg/​kg DM).

Species-spe​cific analy​sis re​vealed that eel​grass (Zostera ma​rina) con​tained sig​nif​i​cantly higher cad​mium con​cen​tra​tions than fil​a​men​tous red al​gae species (Ce​ramium and Poly​si​pho​nia spp.). Avoid​ing eel​grass-rich beach-cast by sea​sonal tim​ing of har​vest​ing and mon​i​tor​ing dif​fer​ences in cad​mium con​cen​tra​tions be​tween har​vest​ing sites could thus fa​cil​i​tate use of beach-cast as biofer​tiliser.

DOI: https://doi.org/10.1016/j.ocecoaman.2018.11.015