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.

Chlorella variabilis and Micractinium reisseri sp. nov. (Chlorellaceae, Trebouxiophyceae): Redescription of the endosymbiotic green algae of Paramecium bursaria (Peniculia, Oligohymenophorea) in the 120th yearp re_579 188..201 SUMMARY Symbiotic algae of the ciliate Paramecium bursaria (Ehrenberg) Focker are key species in the fields of virology and molecular evolutionary biology as well as in the biology of symbiotic relationships. These symbiotic algae were once identified as Zoochlorella conductrix Brandt by the Dutch microbiologist, Beijerinck 120 years ago. However, after many twists and turns, the algae are today treated as nameless organisms. Recent molecular analyses have revealed several different algal partners depending on P. bursaria strains, but nearly all P. bursaria contains a symbiont belonging to either the so-called 'American' or 'European' group. The absence of proper names for these algae is beginning to provoke ill effects in the above-mentioned study areas. In the present study, we confirmed the genetic autonomy of the 'American' and 'European' groups and described the symbionts as Chlorella variabilis Shihira et Krauss and Micractinium reisseri Hoshina, Iwataki et Imamura sp. nov., respectively (Chlorellaceae, Trebouxiophyceae).

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Abstract:The armored dinoflagellate genus Heterocapsa is composed of relatively small species, including a species responsible for harmful red tides, H. circularisquama. Some Heterocapsa species such as H. rotundata and H. triquetra have been well documented as red tide-forming species, but are not recognized as causing harmful effects. Following sequential shellfish mass mortalities in the coastal waters of western Japan due to H. circularisquama red tides, this species has attracted considerable interest. Many properties of this species, such as its distribution and growth characteristics, have been investigated to better understand the mechanisms involved in harmful red tide formation. Related to the need for unambiguous identification of H. circularisquama, several unidentified (or undescribed) Heterocapsa species, which must be distinguished from the harmful taxon, have been detected sympatrically in regions where H. circularisquama blooms occur. However, the taxonomic affiliation of these Heterocapsa species have not yet been determined because several characteristics of Heterocapsa (e.g. body scale ultrastructure) have not yet been reported from all described species due to the changing taxonomic criteria. After the taxonomic ambiguities in this genus were resolved, cellular and body scale morphology of Heterocapsa were reinvestigated and several new species were described. In the present paper, the taxonomic history and morphological characters of the genus Heterocapsa are summarized.

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