Are Starfish Decomposers?

Starfish-eating-mussels

Starfish are a very interesting group without a true brain or heart but still being predators. So, are they ocean decomposers or only consumers? In this blog post, we’ll talk all about that but let’s begin with a quick answer:

Starfish are decomposers because they eat organic matter. They break down dead animal or plant matter and recycle nutrients back into the environment.

However, that certainly doesn’t tell the whole story. Below I’ll explain more about why starfish are decomposers, what else they eat and what are the other decomposers in the ocean. Furthermore, I’ll also explain whether starfish are producers or consumers. Read on!

Are starfish decomposers? (Explained)

Starfish are classified as decomposers because they eat dead organic matter. They move around rocks or sandy bottoms and consume the organic matter by using their mouths and stomachs. Next, the nutrients are put back into the environment.

Because they live on the organic wastes, starfish and other decomposers are considered to be the “cleaning crew” of any ecosystem. These organisms carry out the decomposition process, which means they help to recycle nutrients back into the environment, and the cycle continues with other animals using the nutrients.

Through decomposition, decomposers play a significant role in the food chain. Without them, the organic matter would pile up, and its nutrients would go to waste. Next, organisms at the beginning of the food chain wouldn’t complete the processes or survive, destroying the entire chain balance.

Interestingly, other members of the phylum Echinodermata to which sea stars belong are decomposers as well. These members are the following: sea cucumbers, brittle stars, sea urchins, sand dollars, and crinoids.

Echinoderms are mostly found in shallow tropical waters, such as coral reefs, intertidal rock pools, or kelp forests but can also be found in deeper waters. Here you can read more about where starfish live.

Starfish diet, however, is not only dead organic matter. These animals are primarily carnivores and prey on mollusks, but some starfish species, such as granulated sea stars (Choriaster granulatus) are exclusively decomposer species.

Decomposer Sea Star
Granulated Sea Star

Granulated sea star lives primarily in a sandy habitat rich in detritus, dead animals, and algae. If you want to learn what else sea stars eat, check out my other blog post, “What Do Starfish Eat?”.

Are starfish consumers? (Explained)

Besides being decomposers, starfish are also secondary consumers of the ocean ecosystem. They’re carnivores (feed on other animals) or corallive (feed on coral polyps). Their favorite food is mollusks such as clams, mussels, and oysters.

Consumers are animals that eat other organisms since they can’t produce their own food like producers, which we’ll talk about later. In a marine food web, we can divide consumers into herbivores and carnivores, then further categorize them into primary, secondary, and tertiary consumers.

Primary consumers are herbivores which means they feed on phytoplankton, algae, seaweed, etc. Examples of primary consumers are sea urchins, zooplankton, shrimps, some snails, some crabs, green sea turtles, herbivorous fish, whales, etc.

Secondary consumers are mainly carnivores, which means they prey on other animals, but omnivores who feed on plants and animals are also included. Examples of secondary consumers are predatory fish, seals, whales, squid, some crabs, lobsters, and – sea stars.

Tertiary consumers are usually animals on top of food chains and can be carnivorous or omnivorous, and they feed on secondary and primary consumers. Examples of tertiary consumers are killer whales, dolphins, sharks, some sea birds, etc.

Are starfish producers? (Explained)

Starfish are not producers because they don’t produce their own food.

Producers are an essential base level of any marine food web. They can make food on their own through a process called photosynthesis which means they convert energy from the sun into food. Examples of producers are phytoplankton, seagrasses, seaweeds, and algae.

What are decomposers?

These organisms carry out the decomposition process, which means they help to recycle nutrients back into the environment, and the cycle continues with other animals using the nutrients.

Through decomposition, decomposers play a significant role in the food chain. Without them, the organic matter would pile up, and its nutrients would go to waste. Next, organisms at the beginning of the food chain wouldn’t complete the processes or survive, destroying the entire chain balance.

Interestingly, the distribution of organisms in oceans is uneven because of different conditions, temperatures, depths, light, and more. In general, life is more abundant in warmer and shallower waters. Thus more organic waste and decomposers are found in shallow tropical oceans than in deeper and colder waters.

What are the other decomposers in the ocean?

Decomposers vary in the oceans, as some decomposers thrive in the cold waters of the Arctic Ocean, and others can survive only in warmer waters of the Pacific.

Interestingly, their distribution in oceans is uneven because of different conditions, temperatures, depths, light, and more. In general, life is more abundant in warmer and shallower waters. Thus more organic waste and decomposers are found in shallow tropical oceans than in deeper and colder waters.

The principal decomposers in oceans are bacteria. Other important decomposer organisms are fungi, marine worms, echinoderms, crustaceans, and mollusks.

Bacteria

Bacteria is the most common decomposer in the oceans. Just like bacteria on land, it can be found everywhere and can survive in all sorts of environments. Bacteria play an essential role in the decomposition process because it works straight away when plants or animals die.

Fungi

Fungi are another vital decomposer because, like bacteria, they can survive in colder climates or Arctic or Atlantic oceans. Together, they’re the only decomposers in the cold, the extreme conditions. They vary in size from microscopic to small animals. The smaller fungi help decompose matter, while the larger ones filter out the nutrients.

Marine worms

Marine worms such as Christmas tree worms, feather duster worms, or fireworms crawl around the seafloor, eating the dead matter. They live in shallow waters of coral reefs or intertidal rock pools.

These marine worms spread their long appendages and catch small organic particles. This way, they filter organic matter and create more nutrients for the ocean ecosystem.

Echinoderms

Echinoderms are the animals I already mentioned, and they include sea stars, brittle stars, sea urchins, sea cucumbers, crinoids, and sand dollars. They primarily live in shallow waters, like coral reefs and intertidal rock pools, but some live in deeper waters as well.

Some of the echinoderms are filter feeders and absorb suspended matter and food particles from water by passing water over a specialized filtering structure. Suspension feeders capture floating food particles, and others called grazers, like sea urchins, scrape the food from rocks.

Crustaceans

Crustaceans are a diverse group of invertebrates, including crabs, shrimp, lobsters, krill, prawns, and more sessile creatures like barnacles. They live in every part of the ocean, and some even in freshwater.

Smaller species like barnacles mostly eat organic particles suspended in the water, while larger species such as crabs or lobsters will also eat fresh food like small fish or other crustaceans.

Mollusks

Mollusks include snails, mussels, clams, oysters, scallops, and squid. Sessile mollusks are filter feeders that feed on small organic particles suspended in the water. Most mollusks prefer shallower waters of intertidal pools or coral reefs.

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