Date of Award

2023

Document Type

Thesis

Degree Name

Doctor of Philosophy in Maritime Affairs

Specialization

Ph.D (Maritime Affairs)

Campus

Malmö, Sweden

Country

Barbados

First Advisor

Francis Neat

Second Advisor

Hazel Oxenford

Abstract

Pelagic sargassum blooming in the Tropical Atlantic has been linked to the mass shoreline inundations observed over the last decade in Caribbean and West African countries. Since the onset in 2011, affected countries have and continue to experience multiscale impacts across fisheries, tourism, nearshore coastal ecosystems, maritime transport and public health. Impacts associated with influx events have generated significant economic damage across the region. Moreover, clean-up efforts in response to mass shoreline strandings placed further strain on national economies and in some instances amplified the negative environmental effects caused by inundations. Evidence suggests that influx events are likely to continue into the foreseeable future leaving countries with no choice but to adapt to their new reality. In an attempt to ‘turn the tide’ against influx events, researchers and entrepreneurs are searching for innovative applications for the large quantities of sargassum arriving on their shores. Whilst valorisation of pelagic sargassum presents an opportunity to ameliorate some of the economic damage generated from influx events; commercialization efforts face key constraints that must be overcome in order to turn the current threats associated with influxes into opportunities. Constraints associated with sargassum valorisation can be grouped into five broad categories: (1) unpredictable supply (of sargassum and its different morphotypes); (2) insufficient knowledge of the biological and chemical properties including micro-pollutants; (3) harvesting, transport and storage; (4) governance; and (5) funding. The main focus of this thesis is to understand the spatiotemporal variation in the biological and chemical composition of sargassum influx events. The research takes a compilation approach centring each of the five core papers on knowledge gaps relating to key valorisation constraints. Specifically, this research focussed on understanding: the biodiversity associated with sargassum influx events and identifying implications for in-water harvesting; the variation in the supply of sargassum morphotypes; and the arsenic levels and arsenic ‘species’ composition associated with influx events. Using a combination of quantitative research methods this thesis provides important baseline information on the sargassum community, its morphotypes and arsenic content. Biodiversity assessments indicate that there is a low species diversity associated with shore bound pelagic sargassum. Furthermore, raft size and distance from shore was positively correlated with species abundance. This suggests that in-water harvesting of smaller mats and those within the nearshore environment is unlikely to have any significant negative impacts on the associated community. Assessment of the morphotype composition over the course of one year reveals that variation in the predominant morphotype during influx events is linked to oceanic sub-origins within the Tropical Atlantic. Contrastingly, arsenic analyses suggest that arsenic contamination of pelagic

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sargassum arriving in Barbados was not affected by sub-origins, sample month or year. However, results indicate that the toxic inorganic arsenic species represents a substantial percentage of the total arsenic content of sargassum arriving in Barbados. Findings of this research contribute to the growing body of knowledge on pelagic sargassum influx events in the Caribbean and are relevant to the budding sargassum industry and ultimately to the adaptation of Caribbean people to this new hazard.

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