Macroalgae are the source of many harmful allelopathic compounds, which are synthesized as a defense strategy against competitors and herbivores. Therefore, it can be predicted that certain species reduce aquaculture performance. Herein, the allelopathic ability of 123 different taxa of green, red, and brown algae have been summarized based on literature reports. Research on macroalgae and their allelopathic effects on other animal organisms was conducted primarily in Australia, Mexico, and the United States. Nevertheless, there are also several scientific reports in this field from South America and Asia; the study areas in the latter continents coincide with areas where aquaculture is highly developed and widely practiced. Therefore, the allelopathic activity of macroalgae on coexisting animals is an issue that is worth careful investigation. In this work, we characterize the distribution of allelopathic macroalgae and compare them with aquaculture locations, describe the methods for the study of macroalgal allelopathy, present the taxonomic position of allelopathic macroalgae and their impact on coexisting aquatic competitors (Cnidaria) and herbivores (Annelida, Echinodermata, Arthropoda, Mollusca, and Chordata), and compile information on allelopathic compounds produced by different macroalgae species. This work gathers the current knowledge on the phenomenon of macroalgal allelopathy and their allelochemicals affecting aquatic animal (competitors and predators) worldwide and it provides future research directions for this topic.

Allelopathy is a prevalent natural phenomenon in aquatic ecosystem. We reported the effects of the green macroalga Ulva intestinalis L. collected from estuaries of the Baltic Sea (Poland) on the growth and chlorophyll fluorescence of common filamentous cyanobacterium Nostoc sp. It was found that the addition of 50 µL mL–1 extracts obtained from U. intestinalis inhibited growth of cyanobacterium and after one week of exposition the reduction was 35% of initial amount of Nostoc sp. In addition, we demonstrated that on the seventh day of the exposition, the values of Fv/Fm of target cyanobacterium after addition of 100 µL mL–1 extracts obtained from U. intestinalis was reduced to 49%, compared to control treatment. These results showed for the first time the allelopathic activity of U. intestinalis on Baltic filamentous cyanobacteria Nostoc sp.

Macroalgae can directly restrict the growth of various phytoplankton species by releasing allelopathic compounds; therefore, considerable attention should be paid to the allelopathic potential of these organisms against harmful and bloom-forming cyanobacteria. The main aim of this study was to demonstrate for the first time the allelopathic activity of Ulva intestinalis on the growth, the fluorescence parameters: the maximum PSII quantum efficiency (Fv/Fm) and the effective quantum yield of PSII photochemistry (ΦPSII), the chlorophyll a (Chl a) and carotenoid (Car) content, and the microcystin-LR (MC-LR) and phenol content of three bloom-forming cyanobacteria, Aphanizomenon sp., Nodularia spumigena, and Nostoc sp. We found both negative and positive allelopathic effects of U. intestinalis on tested cyanobacteria. The study clearly showed that the addition of the filtrate of U. intestinalis significantly inhibited growth, decreased pigment content and Fv/Fm and ΦPSII values of N. spumigena and Nostoc sp., and stimulated Aphanizomenon sp. The addition of different concentrations of aqueous extract also stimulated the cyanobacterial growth. It was also shown that the addition of extract obtained from U. intestinalis caused a significant decrease in the MC-LR content in Nostoc sp. cells. Moreover, it the phenol content in N. spumigena cells was increased. On the other hand, the cell-specific phenol content for Aphanizomenon sp. decreased due to the addition of the filtrate. In this work, we demonstrated that the allelopathic effect of U. intestinalis depends on the target species’ identity as well as the type of allelopathic method used. The study of the allelopathic Baltic macroalgae may help to identify their possible role as a significant biological factor influencing harmful cyanobacterial blooms in brackish ecosystems.

Morze Bałtyckie jest wyjątkowym ekosystemem wodnym, charakteryzującym się wyraźnymi zmianami w środowisku, szczególnie w odniesieniu do zasolenia i klimatu. Jest to także miejsce występowania morskich i słodkowodnych organizmów roślinnych, które od stuleci fascynują naukowców. Niewiele jest jednak prac prezentujących bałtyckie glony makroskopowe, jako potencjalne źródło dla zastosowań komercyjnych. Celem niniejszego opracowania było przedstawienie bałtyckich makroglonów, jako źródła zasobów przemysłowych. W przeglądzie uwzględniono, m.in. potencjał wykorzystania tych organizmów w przemyśle kosmetycznym i medycznym, w tym najważniejsze składniki, które czynią je cennym produktem spożywczym. Zwrócono także uwagę na ich rosnącą popularność i potencjalne wykorzystanie w przyszłości, np. jako biopaliwa, nawozy naturalne lub składniki oczyszczalni ścieków. Przedstawiono także możliwość wykorzystania makroglonów jako biologicznego czynnika, ograniczającego występowanie masowych zakwitów sinic w Morzu Bałtyckim.

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