The secret life of the reef: the roles of benthos and zooplankton.
Chapter Two
Habitat and Adaptations
Zooplankton are found in a wide range of aquatic environments, from the surface to the ocean depths. To survive in these diverse habitats, zooplankton have developed unique adaptations, such as mechanisms to regulate buoyancy and advanced sensory systems for finding food or avoiding predators.Zooplankton plays a fundamental role in aquatic ecosystems .
It is a key component of the marine food chain, but at the same time it actively participates in the nutrient cycle and has an extremely significant impact on the dynamics and health of the ecosystems in which it lives.
Now that we have brought some order to the definitions, let's analyze the practical aspect.
The introduction of benthic fauna and zooplankton into the system mainly aims at 3 fundamental objectives :
- Biological pest control and control strategies
- Substrate colonization and biological niche occupation
- Debris disposal and nutrient reduction
- Food function
Biological control strategies in the marine reef aquarium: competition and ecological balance.
Natural pest management in a marine reef aquarium requires a careful biological approach, taking advantage of natural relationships between different species.
The presence of specific benthic organisms and zooplankton can significantly help control and limit the growth of cyanobacteria, bacterial clumps and unwanted algal blooms.
The grazing
In the context of marine biology, the term " grazing " refers to the act of feeding by organisms that consume algae, microorganisms, and algal/bacterial biofilms present on the surfaces of the substrates they colonize .
This practice is fundamental to maintain the balance of marine ecosystems and can have several ecological implications and a major influence on the structure of aquatic communities.
Thanks to “grazing”, algae-eating benthic organisms such as molluscs, crustaceans and echinoderms keep solid substrates clean and aerated, keeping algal populations under control , preventing excessive proliferation and constantly removing algal/bacterial biofilms that form on rocks and sand.
This balance prevents excessive colonization of the substrates by unwanted algae and thick biofilm-forming microorganisms, which could otherwise suffocate the corals and create biological imbalances in the system.
Their action therefore prevents the dominance of certain species of algae, flagellated protozoa and excessively fast-growing bacteria, allowing for greater biodiversity and promoting aquarium stability.
Grazing also helps the proper cycling of nutrients in a marine ecosystem.
Organisms that feed on algae and bacterial biofilms help break down this matter and recycle its nutrients , making them available to other organisms in the ecosystem.
Substrate colonization and biological niche occupation
In the marine reef aquarium, the colonization of substrates and the correct occupation of ecological niches are fundamental processes to ensure the health and stability of the ecosystem.
An effective colonization of the rocks by benthic fauna actively contrasts the presence of algal patinas and bacterial agglomerates.
Considering that currently (and even more so in the future), many tanks are started with sterile sand and rocks, these processes take on even greater importance.
Organisms such as worms, small crustaceans and other benthic invertebrates play a crucial role in bioturbation and nutrient transport within substrates.
This absolutely fundamental process improves the aeration of the substrates, the recirculation of nutrients and prevents the formation of dangerous anoxic zones.
Similarly, the colonization of the substrate and the occupation of ecological niches by beneficial organisms is essential for the control of unwanted organisms.
A large biodiversity of organisms occupying different ecological niches ensures a better distribution of resources, better biological control and better disposal of organic nutrients.
Additionally, the occupation of specific ecological niches by certain organisms helps to naturally control the population of numerous unwanted algal and bacterial species, preventing them from overgrowing and colonizing the entire system.
A richly colonized substrate provides a more stable and resilient environment, capable of reacting better to any imbalances.
Debris disposal and nutrient reduction.
As you well know, one of the most important aspects of managing a marine reef aquarium is nutrient control.
Here too, correct colonization of the substrates is essential, especially in the early stages of the nutrient cycle, when organic debris is still in the form of organic residues.
Macro, meso and microbenthos play a key role in this phase of nutrient cycling.
These organisms break down organic debris, transforming it into simpler forms that can be used by other aquarium inhabitants.
This decomposition process is vital for the natural cycles of organic matter transformation and allows the first transformations to be speeded up, facilitating the subsequent work of the bacteria and the filtering system.
Solid organic particulate matter, on the other hand, is retained and used by filter feeders and detritivores.
By feeding on suspended particles and debris, they actively contribute to the transformation of suspended biomass and reduce the presence of decomposing organic residues.
These organisms (which include sponges, bivalves, worms and numerous other invertebrates ) are also essential in reducing the nutrient load in the aquarium before they are mineralized and converted into nitrates and phosphates.
Food function
Last but not least, the nutritional function of benthos and zooplankton.
We all know that the corals commonly hosted in our systems can rely on both an autotrophic metabolism (thanks to the symbiosis with zooxanthellae) and a heterotrophic one , with the predation of zooplankton.
In nature, every night, corals find themselves immersed in a teeming bath of small planktonic organisms, with a density that is difficult to imagine.
This "rain" of zooplankton in surface waters is a natural phenomenon known as diurnal vertical migration, in which huge quantities of zooplankton rise to the surface as the sun goes down .
In a marine reef aquarium, zooplankton, benthos and the larvae of benthic organisms take on a feeding role similar to that which occurs in nature, being excellent food sources for both corals and fish .
Zooplankton are an extremely nutrient-rich food source for many aquarium inhabitants.
Similarly, many benthic organisms, and in particular their larvae, are an essential part of the diet of numerous fish and invertebrates both in nature and in a reef aquarium.
The constant presence of zooplankton and larvae of benthic organisms helps to replicate the dynamics of the natural environment, providing the organisms with a varied and complete diet.
This biodiversity also helps to meet the different nutritional needs of particular species, promoting the growth and resistance of both coral colonies and planktonic organisms with particular feeding habits such as small gobies, signatids or callionomids.