Assessing the risk to aquaculture from Harmful Algal Blooms (HABs)

Harmful Algal Blooms (HABs) occur worldwide with regionally based differences in their<br/>occurrences. Some of these events have human health consequences due to associated<br/>shellfish poisoning symptoms after consumption of contaminated organisms. Negative<br/>economic implications from HABs also occur for shellfish and finfish aquaculture associated<br/>industries and coastal communities. Understanding temporal and spatial patterns of HABs in<br/>coastal areas of Scotland is required to support the aquaculture industry and its insurers. The<br/>use of long-term data series comprising phytoplankton data and extrinsic variables<br/>(climatological, environmental, fish farm biomass) was undertaken to identify countrywide<br/>patterns and assess the relationships that improve the understanding of HAB ecological<br/>dynamics. A range of statistical approaches including descriptive analyses, spatial statistics<br/>and linear models were used to analyse time series of HAB frequency or cell abundance of the<br/>main taxa related to shellfish poisoning (Dinophysis, Alexandrium, Pseudo-nitzschia) and<br/>farmed fish kills (Karenia mikimotoi) in Scotland.<br/>Interannual frequency of HAB occurrence across the time demonstrated there is no increasing<br/>trend in Scottish coastal waters. Seasonality was identified as a crucial component in<br/>regulating the occurrence of HABs, also determining timing, location and scale of blooms<br/>across the country and on a genera specific basis. The non-correlation between phytoplankton<br/>and biotoxin groups underlines their complex interaction and implies different factors might<br/>act to regulate these dynamics. The use of genera level constrains this assessment which<br/>encourages further study at the species level. The low spatial connectivity found in HAB<br/>events, and the diverse temporal-spatial patterns suggested annual and local conditions are<br/>important in regulating these dynamics. The varied relationship between geographical areas<br/>and seasons suggested local conditions play an important role in regulating HABs in Scotland.<br/>Important environmental variables identified were sea surface temperature and wind intensity.<br/>These presented non-linearity in specific study areas and explained a proportion of cell<br/>response. The highest risk of blooms occur during summer months, with the Shetland Islands generally experiencing a higher frequency in comparison with other areas. Assessing the<br/>relationship of farmed fish biomass (proxy for nutrient loading in the water column) indicated<br/>a lack of relationship with taxa impacting shellfish farms and human health, and Karenia<br/>mikimotoi affecting farmed fish. The production of a risk index including ‘hazard’, ‘exposure’<br/>and ‘vulnerability’ components was useful to estimate the overall risk and assess the<br/>contribution of each component in a socio-economic context, both globally and within a<br/>Scotland based case study. The highest socio-economic risk was identified in the Shetland<br/>Islands, Orkney and Outer Hebrides, mainly related to high dependability on fish farming of<br/>the population in the Islands.<br/>These findings highlight the complex interaction of blooms with extrinsic variables,<br/>suggesting local conditions or stochastic mechanisms are likely relevant in explaining HAB<br/>ecological mechanisms. These results support the robust and localised monitoring of<br/>phytoplankton and biotoxins that pose a threat for the development of the Scottish aquaculture<br/>industry, indicating useful sites for preliminary warnings.

Name dc:type.qualificationname

Doctor of Philosophy (awarded by UHI)

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of the Highlands and Islands

Year dc:date.issued

2023

Author dc:creator

• Gianella, Maria de Fatima

Advisors dc:contributor.advisor

• Davidson, Keith
• Burrows, Michael

Language dc:language

eng

Identifier

oai:pure.atira.dk:studenttheses/3520899d-36a4-4888-930f-35ffb4357509

OAI identifier oai:identifier

oai:pure.atira.dk:studenttheses/3520899d-36a4-4888-930f-35ffb4357509