Changes in the Brown Seaweed Ascophyllum Nodosum (L.) Le Jol. Plant Morphology and Biomass Produced by Cutter Rake Harvests in Southern New Brunswick, Canada

Abstract

Changes in the brown seaweed Ascophyllum nodosum (L.) Le Jol. plant morphology and biomass produced by cutter rake harvests in southern New Brunswick, CanadaAbstract Shoots and clumps of shoots of the commercial brown seaweed Ascophyllum nodosum ("rockweed") add to the benthic complexity of the intertidal environment, providing an important habitat for invertebrates and vertebrates. To protect the structure of this habitat, management plans for the rockweed harvest of southern New Brunswick include restrictions on gear type and exploitation rates limited to 17% of the harvestable biomass. However, owing to physical and environmental factors, the harvest is not homogeneous, creating patches of exploitation ranging from 15 to 50%.A direct relationship existed between clump vulnerability, weight and length in a controlled harvest at 50% exploitation within 8 m by 8 m plots. At this exploitation rate, the gear rarely impacted clumps below 50 g or 60 cm in length. Clumps larger than 300 g and 130 cm were reduced by up to 55% of their length and 78% of their biomass. The overall impacts of the harvest on intertidal habitat is however of short duration as biomass recovers after a year of the experimental harvest. The rapid recovery is mostly due to a stimulation of growth and branching of the suppressed shoots of the clumps. Some harvested plots showed biomass even higher than initial levels, suggesting an increase in productivity at least during the first year after the harvest.

Ecosystem structure and services in eelgrass Zostera marina and rockweed Ascophyllum nodosum habitats

“…Harvesting does stimulate growth and canopy regeneration with a minimum of 85% biomass recovery within a year (Ugarte et al 2006). This may offset the carbon removed during harvest; however, long-term burial of biomass or detritus and export will likely be reduced.…”

“…Both rockweed and eelgrass beds provide important habitat to a wide range of species including at least 6 commercially important species such as American lobster and Atlantic cod (Anderson et al 2008b, DFO 2008. The effect of patchy rockweed harvesting, as in Atlantic Canada, where 15 to 50% of a patch but no more than 17% of a bed may be harvested (Ugarte et al 2006), may create more edge-like habitat. By decreasing the clump length and biomass (Ugarte et al 2006), harvesting effectively creates a less dense interior and could increase the total abundance and richness of species within rockweed beds.…”

“…The effect of patchy rockweed harvesting, as in Atlantic Canada, where 15 to 50% of a patch but no more than 17% of a bed may be harvested (Ugarte et al 2006), may create more edge-like habitat. By decreasing the clump length and biomass (Ugarte et al 2006), harvesting effectively creates a less dense interior and could increase the total abundance and richness of species within rockweed beds. However, the uncertainty around the effects of rockweed harvesting on the associated community necessitates further research.…”

Efeitos do extrato de Ascophyllum nodosum sobre o desenvolvimento e produção de cultivos

“…Ascophyllum nodosum (L.) Le Jolis destaca-se dentre as espécies de algas marinhas comumente empregadas para esta finalidade (UGARTE; SHARP; MOORE, 2006), e tem sido muito estudada por suas propriedades que incluem desde a promoção de crescimento vegetal ao uso na alimentação humana e animal (COLAPIETRA; ALEXANDER, 2006;DI FAN et al, 2011). É uma alga marrom encontrada nos mares árticos e nas costas rochosas do oceano Atlântico no Canadá e no norte da Europa (COLAPIETRA;ALEXANDER 2006;, onde a temperatura da água não excede 27 °C (KESER et al, 2005).…”

“…A alga marrom Ascophyllum nodosum (L.) Le Jolis destaca-se dentre as espécies marinhas comumente empregadas para esta finalidade (UGARTE et al, 2006). Os bioestimulantes derivados de extratos de A. nodosum são constituídos por vários compostos capazes de estimular o crescimento e desenvolvimento vegetal, induzindo também a tolerância a diversos estresses bióticos e abióticos ZHANG;ERVIN, 2008).…”