Disease Ravages Sea Star Population and Disrupts Marine Ecosystem

In 2013, an alarming phenomenon, known as sea star wasting disease (SSWD), severely impacted 20 sea star species along the North American Pacific Coast, spanning from Mexico to Alaska. The magnitude of this event was unexpected even to those who had witnessed multiple sea star mortalities in the past. Observations from a dive in the early part of 2014 depicted a haunting underwater landscape. Countless Pisaster sea stars were found in a state of severe degradation, idling in places where they would ordinarily be foraging.

This catastrophic event inflicted such a harsh blow to the sea star population that the area remained devoid of them for a considerable period. In the cooler waters to the north, the situation was similarly grim. The population of sunflower sea stars (Pycnopodia helianthoides), one of the few predators of sea urchins in northern California, shrunk to a mere tenth of its original size.

This significant decrease in the number of sea star predators led to an unchecked proliferation of sea urchin populations. Without their natural predators to maintain the ecological balance, the sea urchins ran rampant, causing an 80% reduction in kelp forests. Such an event threatens the equilibrium of the nearshore fisheries and can potentially alter the entire marine ecosystem.

Fortunately, the decade-long puzzle surrounding the cause of SSWD was eventually solved. In their publication in the journal of Nature Ecology & Evolution, a group of researchers led by Prentice et al., pointed to the bacterium Vibrio pectenicida as the culprit behind SSWD. This key discovery not only sheds light on this specific marine disease but also offers a broader understanding of various other diseases affecting marine life.

Interestingly, there is a noteworthy connection between the bacteria and molluscs, a common type of marine food organisms for sea stars. This observation postulates the possibility that SSWD might be a food-borne disease caused by the ingestion of molluscs infected with Vibrio pectenicida.

However, another theory is that the strains of V. pectenicida might have evolved to alter their primary host from molluscs, a type of bivalves, to sea stars. Such a shift in host from one species to another, although unusual, is not entirely inconceivable.

Even if the concept of host-switching across different phyla seems anomalous, it can’t be ruled out. The reason is that the strains of bacteria originating from bivalves, which are found to multiply in deceased sea stars, may possess the ability to evolve and subsequently transmit from one sea star to another.

The discovery of Vibrio pectenicida as the cause of SSWD represents a significant advancement in the quest to understand and combat this devastating disease. However, it also draws attention to the intricate and, sometimes unpredictable, nature of marine diseases.

The near disappearance of certain sea star species due to SSWD and the subsequent ecological consequences serves as a reminder of the delicate balance in marine ecosystems. When the ecological equilibrium is upset, the resulting ripple effects can have severe, and sometimes irreversible, consequences.

The rise in sea urchin populations and the accompanying reduction in kelp forests illustrate the dire potential of a single species decline to destabilize marine ecosystems. Protecting marine life, therefore, is not merely about conserving individual species but maintaining the integrity of entire ecosystems.

In conclusion, the findings of Prentice et al., represent a significant advancement in our understanding of marine diseases. Understanding the causative agent of SSWD, i.e., Vibrio pectenicida, and its potential transmission pathways could provide critical insights for future conservation efforts.

While the discovery provides much-needed answers, it also points to areas requiring further study. The question of whether V. pectenicida strains have evolved to change hosts, and how this might take place, is still open to exploration, promising future avenues for research.

Ultimately, delving into the complexities of marine diseases like SSWD underscores the importance of ongoing research for the preservation of our oceans. The intricate balance of marine ecosystems hinges on our understanding of these diseases and our ability to respond effectively to their outbreaks.