Discovering ecological succession and its importance for the restoration of marine ecosystems

Beneath the surface of the ocean, a continuous process of change and adaptation plays a crucial role in the health and resilience of our seas and oceans: ecological succession. This phenomenon, which reflects the evolution and dynamics of marine ecosystems over time, is essential for understanding and conserving marine biodiversity.

Ecological succession is not just a theoretical concept; it is a tangible reality that is part of many marine conservation and restoration projects. One of these projects is OCEAN CITIZEN, in which SUBMON actively participates. This European project aims to develop a replicable marine restoration protocol that combines habitat, carbon immobilisation, and biodiversity regeneration with social engagement and economic benefits for local communities. Furthermore, in OCEAN CITIZEN, we have the opportunity to witness first-hand how marine ecosystems recover and transform over time.

In this article we will explore ecological succession in the marine environment in depth, highlighting its importance for marine conservation and how projects like OCEAN CITIZEN allow us to understand and appreciate this process.

What is ecological succession?

Ecological succession is a fundamental concept in ecology, and it refers to a process by which the mix of species and habitat in an area changes over time. This change is due to shifts in the presence and relative abundance of different species as time passes over years to centuries. While succession is most often thought about regarding the plant community in terrestrial ecosystems, shifts in the populations of other organisms also need to be re-considered in marine habitats.

The succession process can be seen in many different systems, ranging from the establishment of grasslands after a volcanic eruption, the retreat of glaciers or the rebuild of a coral reef after the destruction of a hurricane in the ocean. After the disturbance, the re-establishment of different species starts the cycle again, replacing one another until a “climax community”—like a mature forest—is reached or until another disturbance occurs.

How does it work?

Ecological succession unfolds in three distinct stages, each contributing to the gradual development of an ecosystem. The initial phase is the Colonising Stage, marked by the arrival of small and very simple species, commonly referred to as pioneer species. These organisms quickly colonise the substrate, exhibiting rapid growth and boasting high reproduction rates.

Examples of species that fit into this stage of succession include Asparagopsis taxiformis, a type of red algae, and the Cymodocea nodosa, a type of seagrass that is only present in the Mediterranean Sea and the Atlantic Ocean. This stage sets the foundation for the subsequent phases of succession.

Cymodocea nodosa, Laura Busquier (UGI)

As the process advances, the Successionist Stage takes centre stage. The ongoing colonisation paves the way for the flourishing of new species, often characterised as late successional species. During this phase, the density and diversity of organisms increase, and the ecosystem experiences a maturation process. Competition among species becomes evident, shaping the community structure as it progresses. In this stage, notable examples of species are the Aplysina aerophoba, which is found in both the Mediterranean Sea and the Atlantic Ocean, and the Gongolaria abies-marina.

Aplysina aerophoba, Clara García (UGI)

The culmination of ecological succession occurs in the Climax Stage, representing the final and stable phase of the ecosystem’s development. This stage is characterised by a mature and balanced ecosystem. During this stage, the “endpoint” of the process is achieved: the climax community. This community will persist until a disturbance occurs. Two examples of species that usually appear in this stage are the Antipathella wollastoni and the Leptogorgia viminalis.

Leptogorgia viminalis, Laura Busquier (UGI)

Notably, the initial species in the Colonising Stage are simple, growing rapidly with prolific reproductive rates. However, as the succession unfolds, larger species enter the scene, establishing a complex web of interactions. Predators become more prevalent in the later stages of succession, particularly when the ecosystem has matured and stabilised.

Factors that can affect the process

Ecological succession might be affected by several factors, which can speed up or decelerate the process. For example, disturbance events, such as storms, hurricanes, or human activities like trawling, can reset the succession process by disrupting established communities. Human-induced disturbances can disrupt natural successional processes and lead to the dominance of certain species. After disturbances, pioneer species may rapidly colonise the area, initiating a new succession sequence.

Some of the most important factors are temperature, nutrients, and climate conditions since they influence the types of species that can thrive in a particular marine habitat. Changes in temperature due to climate change and nutrients because of eutrophication can impact the successional dynamics in the long-term.

Furthermore, interactions between species, including competition, predation, and symbiosis, also shape the structure of marine communities. Succession can also be influenced by how species interact and adapt to each other over time.

Understanding the process of ecological succession in the marine environment is key to the conservation and restoration of marine ecosystems. Projects such as OCEAN CITIZEN provide an excellent platform to study this process as it occurs, allowing us to observe how marine ecosystems recover and change over time. We encourage you to continue discovering this fascinating process on the project’s website (oceancitizen.eu) and social media.