The sand shrimp Crangon crangon is a common and ecologically important species found in sand patches near eelgrass (Zostera marina) meadows. Sand shrimps are well-adapted to life in sandy habitats. Their long, slender bodies and powerful legs allow them to move quickly through the sand, while their excellent camouflage makes them difficult to spot. They are often found near eelgrass meadows, where they use the vegetation for shelter and foraging.

The presence of sand shrimps is an important indicator of the health of eelgrass ecosystems. These habitats are vital nurseries for a variety of marine species, including commercially important fish and shellfish. By studying the behavior and ecology of species like Crangon crangon, scientists can gain important insights into the complex dynamics of these critical ecosystems.

Camouflaged Crustacean: A sand shrimp Crangon crangon blends seamlessly into the sandy habitat near a patch of eelgrass Zostera marina, its adapted body allowing it to move swiftly and evade predators.

The periwinkle Littorina littorea is a common species found in eelgrass (Zostera marina) meadows. These small snails play an important role in the marine ecosystem, serving as a food source for a variety of predators, and contributing to nutrient cycling. Periwinkles are well-adapted to life in intertidal habitats, where they can be found grazing on algae and other microorganisms. Their strong, muscular foot allows them to cling to rocks and other substrates, while their spiral shells provide protection from predators.

Eelgrass meadows provide an important habitat for periwinkles, offering a source of food and shelter. The snails also play an important role in maintaining the health of the eelgrass ecosystem, by consuming algae that can overgrow the seagrass and contribute to its decline. By studying the behavior and ecology of species like Littorina littorea, scientists can gain important insights into the complex dynamics of these critical ecosystems, and develop effective strategies for conservation and management.

Grazing in the Meadow: A periwinkle Littorina littorea feeds on algae in a lush patch of eelgrass, its strong foot allowing it to cling to the substrate, and its shell providing protection from predators.

Longlegged spider crabs (Macropodia rostrata) is a species of crab in the family Inachidae, and it is found in the eastern Atlantic Ocean and the North Sea, including the coastal waters of Sweden. This species has long, slender legs that resemble spider legs, hence its common name. It is typically found in shallow waters and seagrass beds, where it feeds on small invertebrates and detritus.

Observing the behavior of spider crabs in their natural habitat can be a challenging and rewarding experience. These creatures are highly adaptable and can move quickly through the eelgrass, making them difficult to spot. But with patience and a keen eye, it is possible to catch a glimpse of these fascinating creatures, and to gain a greater appreciation for the rich diversity of life in eelgrass ecosystems.

Spiny Hideaways: Two longlegged spider crabs (Macropodia rostrata) blend in among the eelgrass canopy, their spiky exoskeletons providing protection from predators, and their long legs adapted for foraging on small invertebrates in the seagrass habitat.

The Pacific oyster, also known as the Japanese oyster (Crassostrea gigas), is a common and economically important species. These bivalves are prized for their meat and have been cultivated for centuries in many parts of the world. The presence of Pacific oysters in eelgrass meadows can have both positive and negative effects on the ecosystem. While these bivalves can help filter water and cycle nutrients, they can also compete with other species for space and resources, and their dense aggregations can alter the physical structure of the seafloor.

This oyster, is an invasive species in many parts of the world, including Sweden, where it competes with the endemic oyster species. Originally from the Pacific coast of Asia, it was introduced to many parts of the world for aquaculture and has since escaped and established wild populations.

Filter-Feeding Bivalves: Pacific oysters (Crassostrea gigas) in a patch of eelgrass, filter-feeding on small particles in the water, and contributing to nutrient cycling in the marine environment.

Hermit crabs (Pagurus bernhardus) are a common and fascinating species found in eelgrass (Zostera marina) meadows. These crustaceans are known for their habit of using empty shells for protection, as they grow and molt their own exoskeleton. In eelgrass meadows, hermit crabs can be found foraging on a variety of small invertebrates and algae, and seeking shelter among the seagrass blades. These habitats offer a rich and diverse array of food sources, and provide important refuge from predators.

One of the most interesting aspects of hermit crab behavior is their use of shells for protection. As they grow, hermit crabs must find larger and larger shells to live in, and will often compete with each other for the best available options. This can lead to interesting and sometimes comical interactions between individuals, as they jostle for position and defend their chosen shells.

Shell Seekers: A hermit crab (Pagurus bernhardus) scurries through a patch of eelgrass, its borrowed shell providing protection and mobility as it forages on small invertebrates and algae in the seagrass habitat.

Eelgrass (Zostera marina) meadows are complex ecosystem that supports a diverse community of marine life, including the fascinating Pipefish species (Syngnathus sp.). This fish species is known for its unique ability to blend in with its surroundings and seek shelter among the eelgrass blades. This strategy allows the pipefish to avoid detection and seek shelter from the hydrodynamic forces of waves and currents that can make life in the open ocean challenging.

In eelgrass meadows, pipefish is able to find ample food sources, as well as suitable cover and shelter from predators. However, the health and abundance of the eelgrass habitat is essential for the survival of this fascinating fish species. If eelgrass populations were to decline or disappear, the pipefish and other dependent species would be in trouble.

In the Gullmars fjord, near Kristineberg these species are common; broad-nosed pipefish (Syngnathus typhle), greater pipefish (Syngnathus acus), straightnose pipefish (Nerophis ophidion), lesser pipefish (Syngnathus rostellatus), snake pipefish (Entelurus aequoreus).

Master of Camouflage: Pipefish species (Syngnathus sp.) seeks shelter among the eelgrass canopy, its body mimicking the shape and color of the seagrass blades. This remarkable fish species relies on the eelgrass meadow for food and shelter, highlighting the importance of protecting these fragile habitats.

The common cockles (Cerastoderma edule) are filter feeders that obtain their food by pumping water through their gills and trapping small particles, such as plankton and detritus. They are also important prey items for a variety of predators, including birds, fish, and crabs. In eelgrass meadows, cockles can be found burrowed in the sediment. They play an important ecological role, as they help to cycle nutrients and provide food for other species. In addition, the cockle is also valued for its culinary uses and is a popular seafood item in many countries.

These cockles have a relatively rounded shell that can grow up to 5 cm in length. It typically lives buried in the sediment of intertidal mudflats and sandy beaches. The species is known for its high tolerance to environmental stress, including low oxygen levels, and is often used as an indicator of the health of intertidal ecosystems.

Hidden Treasure: The cockle (Cerastoderma edule) finds a home among the eelgrass, its shell camouflaging with the sandy sediments. This fascinating bivalve species is a vital player in the local food web.

Shore crabs Carcinus maenas are opportunistic feeders that consume a variety of prey items, including small fish, crustaceans, and mollusks, eelgrass shoot and eelgrass seeds. They are also known to graze on algae and detritus, making them important scavengers and nutrient cyclers in the eelgrass ecosystem. In the eelgrass habitat, shore crabs can be found hiding among the seagrass blades, using their cryptic coloration to blend in with their surroundings. They are an important prey item for a variety of predators, including larger fish, birds, and mammals.

While shore crabs are a valuable component of the eelgrass ecosystem, they are also considered an invasive species in many regions outside of their native range. For example, is endemic in North Europe but invasive in North and South America, Australian and South Africa. This is due to their highly adaptable nature and ability to outcompete native species for resources. Therefore, it is important to manage and monitor the populations of shore crabs in eelgrass habitats to ensure that their impact on the ecosystem is sustainable and balanced.

A Cryptic Resident: The shore crab or green crab (Carcinus maenas) hides among the eelgrass leaves. This adaptable crab species plays an important role in the eelgrass ecosystem, but also has the potential to disrupt native ecosystems outside of its native range.

Shore crab Carcinus maenas in eelgrass.

Eelgrass meristem eaten by the shore crab Carcinus maenas.

The macroalgae Chorda filum is a common sight in the shallow areas that are wave-sheltered between 1-2m depth in eelgrass meadows of Sweden during the summer months. This green seaweed species can grow up to several meters in length and is an important component of the eelgrass ecosystem. Chorda filum provides important habitat and food for a variety of marine life, including small fish, crabs, and sea urchins. It also plays a vital role in maintaining the ecological balance of the eelgrass habitat, by cycling nutrients and stabilizing the sediments.

In addition to its ecological importance, Chorda filum also has a number of potential commercial and industrial uses. It is rich in carbohydrates, making it a potential source of biofuels or other industrial products. It is also used in traditional medicine and cosmetics in many cultures around the world.

An Underwater Forest: The macroalgae Chorda filum is a common sight in the eelgrass meadows of Sweden during the summer months.

The epiphytic ascidian Ciona intestinalis is a small, filter-feeding invertebrate is often found attached to the leaves or stems of eelgrass, where it feeds on planktonic particles in the water. It can be observed in deep wave-sheltered eelgrass meadows in the Gullmarsfjord near Kristineberg marine station.

Interestingly, Ciona intestinalis has been the subject of extensive research in developmental biology, as it has a number of unique features that make it a valuable model organism. For example, it has a simple, transparent body plan that allows scientists to study its internal organs and developmental processes in great detail. It is also an indicator of water quality, as it is sensitive to changes in temperature and pollution levels.

Small but Mighty: The epiphytic ascidian Ciona intestinalis in an eelgrass meadow. This tiny filter-feeder plays an important role in regulating planktonic organisms and providing food for larger predators. It is also an indicator of water quality and a valuable model organism for developmental biology research. Protecting eelgrass habitats is essential for the health of this and many other species.

Ascidia Ciona intestinalis in eelgrass Zostera marina

Eelgrass beds provides a complex and dynamic habitat for a variety of marine species, including many epiphytic organisms. Epiphytes are small, often sessile organisms that attach themselves to the leaves or stems of eelgrass, where they can grow and reproduce. Epiphytic species can include a variety of organisms, such as algae, sponges, bryozoans, hydroids, and tunicates. These species can form complex communities on the surface of eelgrass leaves, creating a diverse and intricate ecosystem such as the colonial ascidian tunicate Botryllus schlosser.

Epiphytic species play an important role in the eelgrass ecosystem, as they can help to regulate the abundance of planktonic organisms, provide a source of food for larger predators, and serve as indicators of water quality. They are also important components of eelgrass biodiversity, contributing to the overall health and resilience of the ecosystem.

However, like many marine species, epiphytic organisms can be negatively affected by environmental change and human activities. Pollution, habitat loss, and climate change can all have negative impacts on their population size and distribution. Therefore, it is important to protect eelgrass habitats and the diverse array of species that depend on them.

Life on the Surface: Eelgrass provides a habitat for many epiphytic organisms such as the colonial ascidian tunicate Botryllus schlosser. These small but important species can form complex communities on the surface of eelgrass leaves, creating a diverse and intricate ecosystem.