My seaweed looks weird

Diseased algae have always been around, but finding one of them in the wild is mostly a chance encounter. Often, the eye of beach-walkers is drawn by seaweeds with an unusual aspect (deformed growth, discolouration, galls, holes or rot symptoms, etc…), but such encounters usually go unreported. “My seaweed looks weird” is a platform where anyone can contribute weird-, or sad-looking seaweeds to accelerate research. With the marine environment undergoing very rapid changes worldwide, and in particular cultivation growing rapidly, we aim to gather a baseline of what diseases occur where, both in the wild and in seaweed farms, in order to be able to detect and monitor any changes.

Our aim is to accelerate the description of algal diseases worldwide, by screening samples submitted by scientists, seaweed professionals or members of the public. We will use the data to identify and map diseases, as well as describe novel or emerging issues. With time, we will make the results of this work available for free, through Open Access publications and a (yet-to-be-built) online disease atlas.

We have provided here a few examples of what diseases may look like, but let’s be honest that most diseases of algae are currently very poorly known. Hence, we welcome your information and your samples, even if you’re not sure whether they’re relevant to us. Using a combination of microscopy and potentially, DNA analysis, we shall endeavour to send you back a diagnosis in-kind for all samples received. Note however that due to the structure of our funding, samples submitted by members of the GENIALG and Global Seaweed Star consortia will be handled in priority. If you are a seaweed farmer, we are very happy to provide you with a diagnosis for free, as and when you suspect problems. However, if you wish us to perform a regular monitoring of your facilities, then please get in touch to discuss options for consultancy.

Twisted stipe and galls on the stipe of Laminaria digitata

Twisted stipe and galls on the stipe of Laminaria digitata

Saccharina latissima showing discoloration, necrosis, hole and dark spot on the full blade

Saccharina latissima showing discoloration, necrosis, hole and dark spot on the full blade

Outgrowths/galls/blisters on the blade of Palmaria palmata

Outgrowths/galls/blisters on the blade of Palmaria palmata

Symptoms of algae diseases

Algae diseases could be caused by two broad factors: environmental and pathogenic. The environmental diseases i.e. abiotic factors are non-infectious and include damage from poor or excessive illumination, freshwater dilution of seawater after heavy rainfall and nutritional deficiencies or toxicities of others algae boom (red/green tide). Algae diseases could be also caused by biotic factors like fishes and invertebrates, grazers feeding on the algae and causing loss of biomass. They could be also caused by many diverse pathogenic microbes: virus, bacteria, fungus, oomycetes, phytomyxeans or even other algal entophytes.

A symptom of algae disease is a visible effect of disease and can give a good clue about the type of pathogens involved. As for plants, symptoms could be a change in the shape or the colour of the alga as it responds to the pathogen even if it is not possible to actually seeing the pathogen himself. 0

Here are a few examples of common signs and symptoms of algae diseases how can affect different parts of the algae (holdfast, stipe, float/gas bladder, blade or the full front/thallus):
– Blister
– Discoloration spot
– Black spot
– Bleaching (whitening)
– Hole
– Malformation and twisted frond
– Twisted stipe
– Gall

Case studies

Case 1: Galls on Laminaria digitata
Case 2: Dark spot on Saccharina latissima
Case 3: Blisters on Palmaria palmata

To contact us, please send an email to: mslw@sams.ac.uk