Food webs in general refer to a complex system of feeding relationships. comprising interconnected food chains. Primarily consisting of trophic levels, including primary producer, primary consumer, secondary consumer, and tertiary consumer, food webs provide us with an inkling as well as certain distinct information regarding feeding patterns in a particular ecosystem and directions of energy and nutrient flow between varieties of species within an ecosystem. In general, a food web may be defined as a collection of food chains in a particular environment.
Primary Producers: The Base of Ocean Food Webs.
Ocean food chains typically start with the primary producers named phytoplankton. Phytoplankton are also commonly known as microalgae and are photosynthetic organisms having chlorophyll. Similar to terrestrial plants in that particular aspect, phytoplankton also require sunlight to grow and are frequently found occupying the upper surfaces of water bodies, in order to make use of the sunlight penetrating the water bodies. The two main types of phytoplankton are diatoms and dinoflagellates, differing based on their morphological structures. Phytoplankton, as an autotrophic organism, functions as the base level in ocean food chains and food webs and acts as a food resource to diverse organisms, including shrimp, snails, and zooplankton.
Primary Consumers: Zooplankton
The next step of the ocean food webs typically consists of zooplankton. Zooplankton refers to the heterotrophic group of plankton consisting of weak swimmers that drift along with the ocean currents. This group most famously includes krill, amphipods, radiolaria, and weak swimmers like jellyfish and Portuguese man o’ war. This group of organisms represents the primary consumer level of an oceanic food web. They then lead the energy and nutritional flow towards secondary consumer level, most generally consisting of small fish such as sardines, herring, menhaden, and small crustaceans, corals, as well as larger organisms such as whales. A notable example of such a phenomenon is the consumption of large amounts of krill by blue whales.
Tertiary Consumers: Apex Predators
The next trophic level of ocean food webs consists of tertiary consumers, also more commonly referred to as apex predators of the oceans. This is due to these organisms not having any natural predators of their own, thus leading for them to dominate the food chains within their particular ecosystem. Apex predators of ocean food webs include sharks, numerous types of whales, seals and larger fish species.
Interconnection and Impacts on Food Webs
“If you’re overfishing at the top of the food chain, and acidifying the ocean at the bottom, you’re creating a squeeze that could conceivably collapse the whole system.”
– Carl Safina
However, just as the above quote suggests, a particular food chain or a species of organisms does not survive alone on its own within an ecosystem. Instead, they are all bound up together in a beautiful
web of life, thus leading to food webs within an ecosystem such as ocean as well. Accordingly, the various phenomena affecting a particular group in the food chain will also be acutely felt by the remaining organisms in the food chain and consequent food web, either positively, leading to a growth in their
numbers, or negatively, leading to a decline in their numbers. For example, a chemical spillage leading to the mass death of secondary consumers would lead to increased population numbers of primary consumers due to lack of predation, while detrimentally affecting tertiary consumers, due to sudden restricted amount of food resources. Either way, an unnatural imbalance would have been created in a natural system. Thus, it is important to note the significance of each animal species within a food web, as a food source for a higher trophic level, or to control the population numbers of lower trophic levels.
The Link Between Ocean Food Webs and Human Lives
On that note, it is vital to recognize how these particular ocean food webs are intricately bound up with human lives as well. In particular, humans function as one of the top predators in these food webs due to the fishery industry. This provides a direct indication that any shifts in balance within the ocean food webs impact humans. Numerous anthropogenic activities cause sudden alterations to population numbers in the food web components at times, leading to a lower number of yields or a yield lower in nutrition for humans at the end of the food web. Chemical or oil spillages and such in the oceans also come back to affect humans via biomagnification and bioaccumulation as well.
“It was the law of the sea, they said. Civilization ends at the waterline. Beyond that, we all enter the food chain, and not always right at the top.”
– Hunter S. Thompson
As quoted from the ‘Generation of Swine’ book by Hunter S. Thompson, mankind must bear in mind that we are not above nature, but are only a part of the intricate web of life woven by nature. This is especially prominent by the fact that humans do not necessarily occupy the topmost positions in the food chains or food webs in the natural world, once outside the boundaries of civilization. Thus, it is not for us to dictate what functions do or do not take place in the environment as well as the rate at which certain phenomena take place. However, unfortunately, it is predominantly anthropogenic activities that lead to the destruction of significant natural orders such as food webs in ocean ecosystems and imbalances in the web of life in general.
Human Influence on Ocean Food Webs
Human activities such as overfishing directly impact marine feeding relationships as they create an imbalance in the numbers of particular fish species, affecting their breeding rates and population numbers, thus causing particular groups of organisms in the food webs to suffer from lack of food resources, while allowing another group to thrive out of control, creating an imbalance in the natural order of systems. Activities such as deep-sea mining also create similar disastrous effects by affecting breeding grounds of particular fish species. This also affects the survival of corals, a detrimental factor in creating imbalances in the food webs of the ocean ecosystems.
Other side effects of fishing industry as well as transport industry via ships and cruisers include chemical pollution and noise pollution which directly and indirectly impacts reproductive cycles of organisms as well as chemical spills leading to damaging of body organs of marine species, leading to decline of particular groups of organisms. Chemical spills in oceans also lead to bioaccumulation and biomagnification, creating disastrous impacts on number of species along the food chain and consequently the food web, for a long time to come. Oil spillages in oceans also lead to death of marine species of plants and animals, creating imbalances in the oceanic food webs. Increased carbon emissions have also led to acidification of ocean waters and consequent warming of ocean waters. Frequent release of land runoff containing agricultural fertilizers and various chemicals lead to the eutrophication of ocean waters, impacting the very base of the ocean food webs, and may lead to deoxygenation of ocean waters. This once again creates detrimental effects on marine species making up the complex food webs of the ocean ecosystems.
Sustainable Practices for Ocean Conservation
Mindful practices when making use of marine resources can go a long way in protecting these ecosystems and maintaining the natural balance of feeding relationships within these ecosystems. Some of these practices include sustainable fishing, where fishery industry is carried on without significantly affecting the fish species of the oceans. Other such measures include establishment of protected areas, as well as ocean habitat restoration, thus ensuring the survival of all the species, leading to balanced oceanic feeding relationships and food webs. However, it is necessary to ensu re that these sustainable practices are carried out continuously and it is vital to implement every possible step from the individual level itself for the better maintenance of ocean ecosystems and food webs.
By: Rtr. Mokshavi Gunasekara
Image credits:
Resources:
- https://education.nationalgeographic.org/resource/marine-food-chain/
- https://www.nature.com/scitable/knowledge/library/food-web-concept-and-applications
- https://oceanconservationtrust.org/ocean-advocacy/think-ocean/ways-to-think-ocean/
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