Infauna – 2 Amazing Information You Need To Know


Last updated on July 23rd, 2022 at 08:36 pm

Infauna are bottom objects that live within the sediments of the seafloor. While the infauna resides in the bottom sediments, those animals residing on the sediments are called the epifauna.

Description of the infauna

Benthic organisms can be classified in various methods. They can be separated according to size, from microfauna to megafauna and from microflora to macroflora; level on the coast, that is, whether they inhabit the supratidal zone, intertidal zone, subtidal or sublittoral zone; movement, that is, whether they are mobile, or sessile; and their position in relation to the sediment.


Some researchers differentiate organisms based upon whether they are moving over the sediment, called mobile hyperbenthic animals, are on the sediment called epibenthos – consisting of the connected epiflora and epifauna and the mobile and sessile epifauna or remain in the sediment infauna.

Without a doubt, the best-studied benthos is the macrobenthos, those kinds bigger than 1 mm (0.04 inch), which are controlled by polychaete worms, pelecypods, anthozoans, echinoderms, shellfishes, sponges, and ascidians. Meiobenthos, those organisms in between 0.1 and 1 mm

What is benthos?

Benthos are the organisms that live at the bottom of the Chesapeake Bay and its rivers and streams. The word benthos originates from a Greek term that means “depths of the sea.” Benthic neighborhoods are complicated and consist of a large range of animals, plants, and germs from all levels of the food web. Clams, worms, oysters, shrimp-like shellfishes, and mussels are all examples of benthic organisms.

The difference between Infauna and Epifauna

Infauna burrow into bottom sediments. Worms, clams, and other infauna form their own neighborhoods or communities that are linked to the water by tunnels and tubes. A healthy infauna community consists of various types.
While on the other hand, Epifauna lives connected to tough surface areas such as pilings, rocks, and shells or directly on the surface of the Bay’s bottom.

Epifauna consists of sponges, oysters, sea stars, sea squirts, and barnacles. An oyster reef is an example of an epifaunal benthic community.

Why are benthic organisms essential?

Benthos plays numerous crucial functions in the food web and act as an exceptional sign of ecological conditions in the Bay and its rivers and streams.

Epifauna - An Amazing Overview

An essential link in the food web

Benthos link main manufacturers – phytoplankton, with greater levels in the food web.

  • Filter feeders such as oysters and clams take in plankton and natural particles.
  • Numerous benthic animals, especially worms and clams, function as food for bigger, financially essential types such as blue crabs, striped bass, area, croaker, and white perch.

Furthermore, the germs, decomposers, and detritus-feeders that live at the bottom of the Bay break down waste items and dead plants and animals.

An ecological snapshot

Due to the fact that they supply a great snapshot of ecological conditions in the Bay and its rivers and streams, scientists have continued to study benthic organisms. If at all, so they can’t prevent contamination or unhealthy water conditions, many benthic animals can not move extremely far.

Benthic communities are exposed to numerous stress factors, consisting of low oxygen levels, excess sediment, and chemical impurities.

  • In the summer season, heats and nutrient contamination typically cause low-oxygen areas at the bottom of the Bay and its rivers.
  • Excess sediment suspended in the water can obstruct sunshine from reaching bay grasses growing at the bottom. When sediment lastly settles, it can bury oyster bars and other benthic types.
  • Numerous chemical impurities bind to bottom sediments, staying there for many years. When they live and feed in these poisonous sediments, benthic types end up being polluted.

Co-working with the Maryland Department of Natural Resources and Virginia Department of Environmental Quality, the Chesapeake Bay Program has actually kept track of the health of benthic organisms in the tidal Chesapeake Bay since around 1984.

Each year, scientists with the Chesapeake Bay Benthic Monitoring Program gather numerous samples and compare the species abundance, biomass, variety, and other credit to conditions that would be anticipated in a healthy environment. The sample outcomes are then scored on a one-to-five scale called the Benthic Index of Biotic Stability, or B-IBI.

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Over the previous years, the health of the bottom environment in the tidal Bay has actually stayed bad. Scientists did observe small enhancements in 2015, nevertheless, with 62 percent of the Bay’s tidal bottom conference repair objectives (compared to 59 percent in 2014). To put it simply, while 38 percent of the tidal Bay’s bottom environment is minimal, abject, or seriously deteriorated – house to more pollution-tolerant types, fewer types in general, less big organisms deep in the sediment, and a lower overall mass of organisms – nearly two-thirds of this environment is house to a healthy neighborhood of benthic organisms.

The level of badly abject and abject conditions was the least expensive it has actually been considering since 1996. Specialists associate this enhancement in the bottom environment with enhancements in liquified oxygen.

Improvements in bottom water quality are believed to be the outcome of low spring river circulation, which indicated lower contaminated overflow streaming into the Bay.

Infauna Benthic Invertebrate Organisms


“Infauna” means marine animals that reside in the substrate of a body of water and which are specifically typical in soft sediments. “Benthic” means anything happening at or in the bottom of a body of water. “Infauna” are the animals that reside in the sediments.

In the Chesapeake Bay, benthic infauna such as clams, snails, polychaetes, flatworms, and little shellfishes, are vital and plentiful to a healthy community.

They assist to filter water, recycle raw material and are essential forage (victim) for fish, reptiles, amphibians, and bigger shellfishes (such as blue crabs and horseshoe crabs). A number of the organisms discovered in the benthos are suspension feeders and deposit feeders.

Suspension feeders, likewise referred to as “filter feeders”, procedure particles drifting in the water column. Deposit feeders take in raw material resting on or in the sediment.

Seasonal changes of types and their abundances can be driven by recruitment (adding individuals to a population), predation, bad environment conditions (such as low liquified oxygen), human effects like coastline hardening, and meteorological occasions like cyclones or hurricanes.

Benthic Infauna in the Rhode River

The Rhode River is a representative tributary of Chesapeake Bay. Macroinvertebrates, such as worms, shellfishes, and mollusks make up the Rhode River’s soft bottom neighborhood. They reside in or on the bottom of the river in mud, sand, clay, marsh sediment, leaf litter, or mixes of these sediment types. Infauna types are accountable for considerable interactions within the benthic environment which in turn, affect the biodiversity and practical procedures within the whole estuarine community.

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Long-lasting information on these types offers us:

  1. information on the species structure and varying abundances of these organisms in time and in varying environments and
  2. a much better understanding of the procedures that control their communities and population characteristics.

Such characteristics consist of predator-prey interactions, recruitment, environment usage, and reactions to ecological elements such as salinity, temperature level, and liquified oxygen.

Incorporating benthic infauna information with our other long term sampling programs supplies insight into procedures structuring environment interactions within the Rhode River

As part of a complicated food web, infauna neighborhoods are made up of both predators and prey. Trophic level (positions in the food web) of these types might alter throughout its life process as the organism grows and its size, feeding system, and dietary requirements change.

Procedures such as bioturbation (sediment disruption) are brought on by infauna burrowing and feeding, specifically by deposit feeder types such as worms or specific types of clams. Bioturbation can, to name a few things, impact oxygen levels in sediments, trigger redistribution and decay of raw material, and modify the number of suspended particles in the water. This, in turn, might adversely or favorably impact water quality, haven patterns, and feeding habits of organisms.

Habitat and ecology


The department and lateral compression of the shell into 2 valves are plainly associated with the adoption of a burrowing mode of life, which is accomplished by a muscular foot. Primitive types were detritivorous, whereas modern bivalves are suspension feeders that gather food particles from seawater using their customized gills called ciliated ctenidia. The burrowing, filter-feeding mode of life limits bivalves to marine environments.

Retention of the larval anchoring byssus into adult life has actually released lots of bivalves from soft substrates, enabling them to colonize the tough surfaces. This has actually likewise been accomplished by cementation, as, for instance, in oysters.

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There are no pelagic bivalves, other than for Planktomya hensoni, which is still benthic as an adult however has an abnormally long planktonic larval phase. Some bivalves can swim, albeit weakly when removed from the sediment, as can some file shells. Real swimming is, nevertheless, seen just in the family Pectinidae (scallops) however is utilized primarily as an escape response.

Lots of agents of the superfamily Galeommatoidea are commensal, a couple of them are parasitic, and both have actually hence ended up being miniaturized.

A lot of bivalves are discovered in seaside seas, however, their variety is biggest on continental landmasses, where big rivers produce appropriate deltaic environments and the continental rack is broad.

Other than on tropical ones with reefs, a couple of bivalves are discovered on islands.

Of the different subclasses, 2 are crucial environmentally: the Heterodonta are modern burrowers that consist of cockles, clams, shipworms, and huge clams and feed mainly on the suspended products. On the other hand, the Pteriomorphia, an older group that is anchored to rocks (epibyssate) controls difficult substrates.

The subclass is comprised of oysters, mussels, jingle shells, and others. A few of their older agents are anchored to the product within a burrow or dugout (endobyssate), exposing their evolutionary history. The majority of these 2 classes inhabit a broad variety of sub habitats, with basic reproductive techniques, external fertilization, and planktonic larvae to impact broad dispersion.

They assign the shallow-water marine domain essentially everywhere. The Palaeoheterodonta (a group that consists of the unionids) are specifically freshwater types, however, all have substantially more complex life processes.