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Global trends in the occurrence, toxicity and risk posed by harmful algal blooms to natural systems, human health and coastal economies are poorly constrained, but are widely thought to be increasing due to climate change and nutrient pollution. Here, we conduct a statistical analysis on a global dataset extracted from the Harmful Algae Event Database and Ocean Biodiversity Information System for the period 1985–2018 to investigate temporal trends in the frequency and distribution of marine harmful algal blooms. We find no uniform global trend in the number of harmful algal events and their distribution over time, once data were adjusted for regional variations in monitoring effort. Varying and contrasting regional trends were driven by differences in bloom species, type and emergent impacts. Our findings suggest that intensified monitoring efforts associated with increased aquaculture production are responsible for the perceived increase in harmful algae events and that there is no empirical support for broad statements regarding increasing global trends. Instead, trends need to be considered regionally and at the species level.

A 2022 special report from Woods Hole Oceanographic Institution, examining the threat of harmful algal bloom growth and the actions being taken to address it.

The Greek coastal waters are subjected to harmful algal bloom (HAB) phenomena due to the occurrence of species characterized as toxic (TX), potentially toxic (PT), and non-toxic, high biomass (HB) producers causing harm at multiple levels.

IRELAND - Record toxic algae blooms continue to close shellfish harvesting in the south west of Ireland are caused in part by the waste from fish farms. The local action group set up to oppose the expansion of fish farming, Save Bantry Bay, has drawn attention to the fact that fish farms are responsible for far more nitrogen and phosphorous in our coastal waters than sewage from major towns.

A study of harmful algae blooms in the Red Sea reveals a potential correlation with activity from the National Aquaculture Group (NAQUA), pointing to a need for a national wastewater management plan that will prevent excessive nutrient overload.

High ocean temperatures helped cause toxic bloom that has wiped out up to 20% of Chile’s total production for the year.

Anthropogenic marine eutrophication has been recognized as one of the major threats to aquatic ecosystem health. In recent years, eutrophication phenomena, prompted by global warming and population increase, have stimulated the proliferation of potentially harmful algal taxa resulting in the prevalence of frequent and intense harmful algal blooms (HABs) in coastal areas. Numerous coastal areas of the Mediterranean Sea (MS) are under environmental pressures arising from human activities that are driving ecosystem degradation and resulting in the increase of the supply of nutrient inputs. In this review, we aim to present the recent situation regarding the appearance of HABs in Mediterranean coastal areas linked to anthropogenic eutrophication, to highlight the features and particularities of the MS, and to summarize the harmful phytoplankton outbreaks along the length of coastal areas of many localities. Furthermore, we focus on HABs documented in Greek coastal areas according to the causative algal species, the period of occurrence, and the induced damage in human and ecosystem health. The occurrence of eutrophication-induced HAB incidents during the past two decades is emphasized.

The Greek coastal waters are subjected to harmful algal bloom (HAB) phenomena due to the occurrence of species characterized as toxic (TX), potentially toxic (PT), and non-toxic, high biomass (HB) producers causing harm at multiple levels. The total number of (TX), (PT) and (HB) algae reported in this work are 61, but only 16 species have been associated with the occurrence of important HABs causing damage in the marine biota and the water quality. These phenomena are sporadic in time, space and recurrence of the causative species, and are related to the anthropogenically-induced eutrophication conditions prevailing in the investigated areas.

Tasmania is regarded as one of the wildest, most pristine states in Australia. In recent years however that reputation has been tarnished by the boom of the local salmon farming industry. With environmental regulations struggling to keep pace with the industry’s growth, the marine environments that host the industry have been significantly impacted and in some cases have approached collapse. Increased scrutiny of the industry – aided by the mobile nature of ocean pen farming – has forced operators to find new locations. When the industry set their sights on opening up a new territory on neighboring King Island – adjacent to the world-class waves of Martha Lavinia Beach – they were unaware they were also picking a fight with surfers worldwide.