#mytilidae

[drhoz]

#2415 - Xenostrobus neozelanicus - Little Black Mussel

AKA Hauea and Flea Mussel, Modiolus ater, Modiolus neozelanicus, and Mytilus ater.

A small mussel found around New Zealand and the Auckland Islands. Like other mussels, a filter feeding bivalve that are usually found in intertidal environments. One genus is found in freshwater, and one subfamily lives in the deep ocean.

Puritutu Rock, New Plymouth, New Zealand.

[rattyexplores]

That's a lot of mussels.

14/10/23 - Mytilidae sp.

QLD:WET - Garner's Beach

[banukai]

GUESS WHAT I FOUND?

THATS RIGHT! Clams, Mussels, and Barnacles! You can find these guys in many places across the Forbidden West but I found these particular ones in the area of The Greenhouse. Remember when I said it was weird that the people of E-9 didn't know what 'shelled marine animals' were?

Cerastoderma edule is a species of marine bivalve mollusc known as the Common Cockle. They're commonly farmed and are eaten across the world. Common Cockles belong to the Cockle family Cardiidae.

Mytilus edulis is a species of marine bivalve mollusc called the Blue Mussel. I love these guys! When my family used to take trips to the coast we would always see a ton of these shells. Blue Mussels are part of the true mussel order Mytilida in the family Mytilidae.

Balanus glandula is a species of crustacean known as the North American Acorn Barnacle. Barnacles have the longest penis (relative to body size) of any animal! They can stretch their penises up to 8 times their body length. Acorn Barnacles belong to the highly diverse acorn barnacle family Balanidae.

[wikimediauncommons]

file: Mussel (Mytilidae) - Oslo, Norway 2020-12-23.jpg

[life-around-me-yura15cbx]

The New Zealand green-lipped mussel (Perna canaliculus), also known as the New Zealand mussel, the greenshell mussel, kuku, and kutai, is a bivalve mollusc in the family Mytilidae (the true mussels). P. canaliculus has economic importance as a cultivated species in New Zealand.

Pauanui Beach, Waikato

XVM8+VW6 Pauanui

-37.0153500, 175.8672580

[crudlynaturephotos]

[dugbus]

A new Michael Johnson getting settled by the shore. Nice piece. Hopefully hefty enough to survive the gfw. #michaeljohnson #sculpture #stainlesssteel #bronze #mytilidae #musselburgh #urbanart #publicart (at Musselburgh, Midlothian)

[13yousuke-blog]

#サンセバスチャン の #シーフード 専門の #バル #lamejillonera 。 いつも超満員のこのお店で食べた #ムール貝 がめちゃ美味い！ 俺的ムール貝史上No.1 #スペイン #サンセバスティアン #ドノスティア #タパス #ピンチョス #旅 #旅行 #spain #sansebastian #donostia #bar #tapas #pintxos #mytilidae #trip #travel (La Mejillonera) https://www.instagram.com/p/BwsU_RQD3hk/?utm_source=ig_tumblr_share&igshid=qncnf7olenqy

[drhoz]

#2416 - Perna canaliculus - New Zealand Green-lipped Mussel 

AKA the greenshell mussel, kuku, and kutai, Mytilus canaliculatus, canaliculus, durus, latus and tasmanicus.

An endemic New Zealand subtidal mussel, grown in huge quantities for the aquaculture industry. Most of the spat is collected from seaweed that washes up on Ninety Mile Beach on the north coast. This spatfall is highly variable - in some years none arrives at all.

In 2000 two companies that were promoting an extract of green-lipped mussel as a cancer cure were successfully prosecuted and fined. Only click on the green-lipped mussel tag below if you want some amazingly badly translated posts about their supposed antioxident properties.

Puritutu Rock, New Plymouth, New Zealand.

[oceansoftheworld]

(Photo/Info)

Mussel is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval. The word "mussel" is most frequently used to mean the edible bivalves of the marine family Mytilidae, most of which live on exposed shores in the intertidal zone, attached by means of their strong byssal threads ("beard") to a firm substrate. Byssal threads, used to anchor mussels to substrates, are now recognized as superior bonding agents. A number of studies have investigated mussel "glues" for industrial and surgical applications. Additionally byssal threads have provided insight into the construction of artificial tendons.  

The common name "mussel" is also used for many freshwater bivalves, including the freshwater pearl mussels. The mussel's external shell is composed of two hinged halves or "valves". The valves are joined together on the outside by a ligament, and are closed when necessary by strong internal muscles (anterior and posterior adductor muscles). Mussel shells carry out a variety of functions, including support for soft tissues, protection from predators and protection against desiccation. Marine mussels are usually found clumping together on wave-washed rocks, each attached to the rock by its byssus. The clumping habit helps hold the mussels firm against the force of the waves. 

In 2005, China accounted for 40% of the global mussel catch according to a FAO study. Within Europe, where mussels have been cultivated for centuries, Spain remained the industry leader. Aquaculture of mussels in North America began in the 1970s. In the US, the northeast and northwest have significant mussel aquaculture operations, where Mytilus edulis (blue mussel) is most commonly grown. While the mussel industry in the US has increased, in North America, 80% of cultured mussels are produced in Prince Edward Island in Canada. In Washington State, an estimated 2.9M pounds of mussels were harvested in 2010, valued at roughly $4.3M.

[encyclopika]

Animal Crossing Fish - Explained #124

Brought to you by a marine biologist and...goddamnit

CLICK HERE FOR THE AC FISH EXPLAINED MASTERPOST!

Wow, here’s another one I missed while it was available in the Northern Hemisphere. It’s fine. I’m fine. So today’s not-a-fish is the mussel, another bivalve mollusk. ACNH features so many different kinds of bivalves because they are super important to people; they are not only a healthy food option, but are also an animal that provides an ecosystem service. 

I’m not going to waste space here explaining what bivalves are again - check out my articles on the Scallop, Oyster, Manila Clam, Gigas Giant Clam, and Pearl Oyster for more facts, because damn do we have a lot to cover. 

True Mussels are in the Order Mytilida within the Bivalve class of Mollusks. They are all typically this shape you see above, are filter-feeders, and, like their cousins the oysters, prefer to sit in the same spot their whole lives as a “mostly” immobile adult. Some mussels live in the deep, dark abyss near black smokers and other semi-permanent habitats down there, but for the most part, mussels are generally coastal, inter-tidal species. The mussel featured in Animal Crossing is most likely a member of the Blue Mussel Complex. I know that sounds like a band name, but let me explain. 

Blue Mussels are typically known scientifically as Mytilus edulis, however, it’s been found that species that look very much like Mytilus edulis are actually other species that occur within the same range and very often hybridize with each other. The complex encompasses at least 3 very closely related taxa, one of which occurs on both sides of the North Pacific, which includes Hokkaido, Japan. I really doubt the ACNH developers thought this hard about this, but in an effort to be really scientific, this is most likely representing Mytilus trossulus, the North Pacific member of the Mytilus edulis complex, also known as the Bay Mussel or Foolish Mussel.  

From this site. This picture is showing a black phase mussel and brown phase mussel, the latter of which is rarer than the former. Obviously, the ACNH model is of the black phase. 

Taxa in the Mytilus edulis complex collectively occur in temperate, coastal areas with lots of hard substrate onto which the mussels can attach themselves via their byssus threads. These threads are made of proteins the mussel secretes. Unlike the oyster, which plants itself in a spot via biological cement, the byssus threads mussels make can be broken and remade. In this way, mussels can move from their spot when it’s no-longer advantageous to be there. 

By Brocken Inaglory, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5309651

Mussels use their byssus threads to make huge aggregations called “mussel beds” in which hundreds to thousands of mussels congregate. They will also attach to plant roots and other hard substances, creating natural wave breakers that protect vulnerable shoreline. Here on Long Island, NY, we are actually having erosion problems because we’ve had a history of stupidly removing mussel beds and other bivalve structures in favor of cement which sucks at stopping storm surge. In this way, mussels, as well as other kinds of bivalves that create structures like this provide what’s called an “ecosystem service”, or very generally, something nature does for free. Our lives really do depend on these ecosystem services. Plant pollination from bees, erosion and flood control from trees, and storm surge protection from bivalves are only some of the things nature does for free that we’d be very screwed without. 

And there you have it. Fascinating stuff, no?

[f107group2]

Time to Flex these Mussels

They say we are what we eat. Bodybuilders must've eaten a lot of mussels then.

Classification

Kingdom: Animalia  

    Subkingdom: Bilateria  

        Infrakingdom: Protostomia  

          Superphylum: Lophozoa  

              Phylum: Mollusca   

                Class: Bivalvia                   

                   Subclass: Pteriomorphia 

                      Order: Mytiloida  

                          Family: Mytilidae  

                            Genus: Mytilus  

                                Species: Mytilus edulis (Linnaeus, 1758) – edible blue mussel, blue mussel (ITIS 2020)

Hanging out with the English

Photo by Guillermo D’Elia (2016)

Just chillin in the northern part of the globe, the Mytilus edulis occurs in the northeast and northwest of the Atlantic Ocean, mostly in Scotland and the British Isles in high intertidal and subtidal zones from estuaries to oceanic waters (CABI 2020; FAO 2020).

Open Sesame: Unraveling the Insides

Photo by DesignPics 

Photo by Rainer Zenz

The main parts of the mussel are its shell and its foot. The shell has 3 layers namely: nacre (mother of pearl) which is continuously secreted by the mantle, prismatic layer, and periostracum which protects the prismatic layer from abrasion. The blue mussel’s shell color is blue, usually purple, and sometimes brown. Its shell is smooth and equivalve (valves of equal shape and size) with concentric lines starting from the hinge. Its hinge line has no teeth but it has 3-12 crenulations under the umbones (Oli 2016).

Photo from: Eggermont et al

Internally, its intestine is continuous to the anus where waste is excreted from the excurrent siphon. It has 2 pairs of gills, each pair resides on each shell valve. Other internal organs include the hepatopancreas, kidney, gonad, and a 2-chambered heart. Its nervous system consists of ganglia or nerve centers because it has no brain or head in their body. Its foot is protruded outside the shell for locomotion and anchoring to substrates (Oli 2016). 

Check out the video below to further know about its anatomy.

Hold On Tahong!

Wonder how mussels are able to anchor themselves?

Interestingly, in the foot of mussels are byssal glands that produce byssal threads. These threads are strong and silky fibers made from proteins and are responsible for anchoring the organism to a substrate. With this, the industrial and medical areas have studied this “glue” which offered on how to create artificial tendons (Kenedy 2019).

Life (and Production Cycle)

Photo from: Science Learning Hub (top), FAO (bottom) 

A bed, not the type you’d sleep on, but reproduction can still happen 👀

As adults, blue mussels are typically found in dense mussel beds. They are broadcast spawners meaning that both have a separate male and female sex and they cast their gametes (sperm and eggs) into the water at the same time and fertilization takes place in the environment. See this video below in which a blue mussel releases its sperm in the water.

The larvae then undergo a series of metamorphosis from planktonic trochophore to veliger until such time it attaches to algae and after some time, joins other mussels.

Since this species is capable of being cultured, instead of settlement on filamentous algae in the wild, they are attached to the ropes and bamboo rafts for the initial settlement during aquaculture and they no longer need a secondary settlement because they are already with other mussels. 

Photo from: GNS Science 

Ecology

If a blue mussels were to submit a resume, it will surely get accepted. Why? They are very versatile!

Blue mussels are capable of withstanding wide fluctuations in salinity, desiccation, temperature, and oxygen tension (FAO 2020). These abilities enable it to occupy a variety of microhabitats and expand its zonation range from high intertidal to subtidal regions, from estuaries to the ocean waters. It can survive in countries with climatic conditions such as mild, subtropical to frequently frozen habitats because they are both euryhaline and eurythermal (FAO 2020)

What’s the Menu to Being the Menu Real Quick

Mussels are often on the seafood restaurants’ menu. But what is on the mussel’s menu? 

They are filter feeders and so any detritus and plankton in the water columns that happen to drift near them can be pulled towards the organism through ciliary actions. Unfortunately, they are not only on the seafood restaurants’ menu but a lot of aquatic organisms also feed on them as well - from sea stars, sea anemones, snails, crabs, fishes,  to diving ducks, northwestern crow, gulls, and sea otters. Maybe their versatility also has its downsides and this is mainly being exposed to a lot of predators.

Photo from: Ruth Foster

However, without mussels that filter the water to take out toxins, algae and debris, the water will not be as clean, and without clean water, fish will have less oxygen causing them to die. Furthermore, they help concentrate the nutrients on lake bottoms and river-beds for other aquatic plants and animals.

Watch this video to see how mussels can help in improving the water quality in terms of turbidity:

Mytilus edulis @ 18: Welcome to Legality

Photo from: British Antarctic Survey 

Most cultured mussels are produced in less than 2 years but in the wild, blue mussels can live up to 18-24 years (FAO 2020), hence its shell growth over the years is a powerful indicator for environmental changes (British Antarctic Survey 2018).

A new study headed by Leca Telesca from University of Cambridge, claims that they have developed a method to accurately describe which specific traits change when facing specific environmental conditions regardless of age, species and other potentially confounding factors (British Antarctic Survey 2018). This is an important feature to track environmental stressors throughout the years.

Connecting with my Hooman

Have you ever tasted a tahong? Umm.. the blue tahong? Cos I haven’t. But they say that the blue tahong’s meat is excellent compared to the green-lipped tahong.  What about you? What KINDS of tahong have you eaten?  👀  

Centuries of Blue Entrée

Mytilus edulis has long been utilized and exploited even way back 6000 BC as scraps of shells were found as kitchen middens (FAO 2020). Blue mussels are harvested as a food source both from the wild and as farmed sources from commercial aquaculture. Blue mussels are a very important food source, especially to the coastal communities. 

DANGER: Toxic Shellfish Ahead

Despite its popularity as a food source, Diarrhetic Shellfish Poisoning (DSP) and Paralytic Shellfish Poisoning (PSP) pose a serious threat to the consumers that often leads to long-term industry closures and human health problems (FAO 2020) These poisonings are caused by harmful algal toxins consumed by the mussel.

Aiding the Economy

Blue mussel is an economically important species in the northwest Atlantic and temperate zones both imported and exported in the U.S. domestic fish market. With exported 2,018,000 lbs ($3.86 million) of all mussel species both wild and farmed harvest in 2013-2014 (The Safina Center 2017).

In the Philippines, the volume of farmed mussels continues to increase with 18, 774 metric tons to 26, 302 metric tons harvested last 2016 and 2018 respectively. (psa.gov.ph)  

Interestingly, blue mussels are not that common compared to green mussels in the Philippines! Hmm… No wonder I haven’t eaten one yet!

Fun Facts Time ! ! !

Yes... We know this is your most awaited... 

1. It was just an accident! 

The introduction of the blue mussel in the Philippines is possibly accidental due to shipping activities according to Philstar.com.

2. It’s an engineer! Yep, mussels are!

 Unlike you. . . they’re an ecosystem engineer.

Mussels are considered to be an ecosystem engineer as they can alter their environments for the better. They filter particles and make the water clean that positively affect their ecosystem and everything else that lives within the ecosystem. 

3. Colorful Comparison

The mantles of lady mussels are orange while gents’ are creamy white. 

4. Sorry SpongeBob We Must Side With Plankton

Mussels feed entirely on plankton. To do this they can filter up to 65 litres of water a day.

5. Gandang Natural! Finger Comb!

Chitin from shellfish such as in mussel is used to make “chitosan” which is found in moisturizers, hair-care products, and medical applications such as wound dressings and as a protective coat for wheat seeds.

 6. Mussels do fish!   …What?

Some species of mussels have to “go fishing” in order to get fish nearby to release their larvae for attachment as their life cycle includes fish as a host. Their mussel larvae attach themselves to the gills of fish, where they develop into juvenile mussels before detaching into the stream or river. To attract fish, mussels have developed very ornate lures that resemble small prey fish (Purdue University).

Check out these videos on how these mussel Lampsilis sp. attract fish.

 Reference:

British Atlantic Survey (2018). Blue mussel shape is a powerful indicator for environmental change. Retrieved October 14, 2020, Available from: https://phys.org/news/2018-02-blue-mussel-powerful-indicator-environmental.html

CABI. (2020). Mytilus edulis (common blue mussel). Retrieved October 15, 2020. Available from:https://www.cabi.org/isc/datasheet/73755#:~:text=trossulus%20occurs%20in%20the%20north,native%20(Wonham%2C%202004). 

Entrepinoys Atbp. Business Ideas Philippines. (2012). Mussel Culture (Tahong). Retrieved October 14, 2020 from  https://ep.franphil.com/mussel-culture-tahong/

FAO (Food and Agriculture Organization). (2020). Mytilus edulis (Linnaeus 1758). Retrieved October 14, 2020. Available from: http://www.fao.org/fishery/culturedspecies/Mytilus_edulis/en#:~:text=Blue%20mussels%20are%20widely%20distributed,%2C%20temperature%2C%20and%20oxygen%20tension. 

ITIS (Integrated Taxonomic Information System). (2020). Mytilus edulis (Linnaeus 1758). Retrieved October 14, 2020. Available from:https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=79454#null 

Kenedy J. (2019). What Is a Byssal Thread?. Retrieved October 14, 2020. Available from: https://www.thoughtco.com/byssal-byssus-threads-2291697 

Oli NA. (2016). Biology of Mussels and Camps. Retrieved October 14, 2020. Available from: https://www.slideshare.net/Nazmuloli52/biology-of-mussels-camps 

Philippine Statistics Authority (PSA). Fisheries Statistics. Retrieved October 14, 2020 from  https://psa.gov.ph/sites/default/files/Fisheries%20Statistics%20of%20the%20Philippines%2C%202016-2018.pdf

Philstar (The Philippines Star). (2015). Blue mussels reach Pangasinan coast. Retrieved October 14, 2020 from https://www.philstar.com/business/science-and-environment/2015/12/30/1537711/blue-mussels-reach-pangasinan-coast

Purdue University. (n.d.). Heart of the Tippy. Retrieved October 14, 2020 from https://www.purdue.edu/extension/mussels/more-about-mussels/

The Safina Center. (2017).  Blue Mussel Mytilus edulis.  Retrieved October 14, 2020 from https://seafood.ocean.org/wp-content/uploads/2017/01/Mussels-Blue-US-Atlantic

THAT’S IT FOLKS. BYE!

[engineeringecosystems]

One mussel, two mussels, brown mussels, blue mussels

Walking through a meadow calling the plants by name is like entering a room of friends instead of strangers. -John Hildebrand

Taxonomy is the science of classifying organisms based on their shared characteristics. Although we probably started purposefully grouping things together around the same time that we developed language, the first physical record of classification dates to around 3000BC in China, with the Father of Chinese medicine, Emperor Shen Nung. It wasn’t until the 1700′s when a Swedish botanist came along and developed the system of classification that we use today. Known as the “father of modern taxonomy”, Carolus Linnaeus dedicated his career to classifying plants and animals (and minerals). Carl’s catalogue was a continuous piece of work, constantly being added to and revised as he identified and classified new organisms. In 1758 Carl published the 10th edition of his massive taxonomic collection in a book titled Systema Naturae - and I mean truly massive, by its 13th edition it was 3000 pages long! 

With the introduction of animals, the 10th edition of Systema Naturae is widely accepted as the start to “modern” taxonomy. Carl classified organisms into a hierarchy - which we know as the Tree of Life. From trunk to leaf, least to most exclusive, it goes: kingdom, phylum, class, order, family, genus and species. Carl also developed and popularized the use of binomial nomenclature which shortened long-winded Latin names down to two terms, the first denoting the genus and the latter the species. However, circumstances of the time heavily influenced Carl to describe the world as created by God which led him to classify organisms based on morphological features, such as the shape, size and placement of bones in a skeleton. This was very helpful at the time because until then we thought whales were fish! But, as technology has progressed, especially in the field of genetics, we began to learn that just because two organisms look alike or behave in a similar manner doesn’t necessarily mean that they’re the same organism, or even closely related, if at all. This, of course, led to a reorganization of Carl’s work (and occasionally to the dismay of stubborn scientists). If you’re keen to learn more about Carl or taxonomy check out this video.

As useful as it is, identifying and classifying organisms can get a bit overwhelming, especially when everything looks the same (yeah, I’m talking about you mussels!). I am going to do my best to break this post down into bite sized pieces. So, without further ado, lets classify some mussels.

I figured it’s probably best to start with the common blue mussel, Mytilus edulis (credit: British Antarctic Survey), first described by Carl in 1758. 

Quick shell fact: although all Mytilus edulis, the shells above are from high to low latitudes (left to right) and show subtle morphological changes due to environmental factors like temperature and salinity.

Despite looking like a rock (there, I said it first so you don’t have to feel bad), Mytilus edulis is an animal, and therefore in the kingdom Animalia. Like many members of the phylum Mollusca, from squids to snails, Mytilus edulis has a radula, a mouthy bit that creates a current drawing in water and food, a fleshy covering that holds their body together called a mantle, and a shell made mostly of calcium carbonate. Mytilus edulis has two shells, or valves, which are held together by a strong muscle called a foot (which also makes them so dang hard to open and eat), situating it among others like clams, scallops and oysters, in the class Bivalvia. We are first introduced to the “true” mussels in the order Mytilida, which are characterized by having long asymmetrical shells covered by a thick, adherent layer of “skin” called the periostracum; they attach themselves to solid substrate, like rocks, rope, or piers, using a secreted bundle of filaments, referred to as a byssus or byssal threads. The only extant (not extinct) family in this order is the family Mytilidae which contains some 52 genera. One of these is the genus Mytilus which contains most of the edible marine mussels. Finally, we arrive at our friend the common blue mussel or the Atlantic blue mussel, known by its species name Mytilus edulis.

And there you go. 

Mytilus edulis occupies the coasts of the North Atlantic, including the United States and Canada, as well as France and the British Isles across the pond. When its range overlaps with others in its genus, like Mytilus galloprovincialis in the Mediterranean or Mytilus trossulus in the northern parts of the North Atlantic, Mytilus edulis will sometimes form a complex and hybridize with them. 

Other members of the genus Mytilus include:

Mytilus californianus, the California mussel (credit: Sharon Mollerus)

Mytilus coruscus, the Korean or hard-shelled mussel (credit: Conchology, Inc.)

Mytilus galloprovincialis, the Mediterranean mussel (credit: Andrew Butko)

Mytilus planulatus, the Australian blue mussel (credit: Javier Couper)

Mytilus platensis or chilensis, the Chilean blue mussel (credit Schnecken & Muscheln)

and Mytilus trossulus, the bay or foolish mussel (credit: Conchology, Inc. ).

I imagine many of you are looking at these mussels and thinking, “yeahhh uhhh Matt, they all look like the same”. Maybe with this face

(or maybe even this one).

But stay with me. 

You’re right, they do look very similar, which is why classification can be troublesome when it’s based off how an organism looks. Classification based off morphological features can be useful, but up to a point, and may be useless at finer-species level-scales. But advances in science and technology have led us into the new age of taxonomy - classification based on genetic sequencing, using a technique called Polymerase Chain Reaction or PCR.  Like reading a recipe, scientists can sequence the genome of an organism and reveal hidden secrets like the evolutionary age of an organism, which can help us construct a more accurate representation of the Tree of Life. Along with advancements like data storage, genetic sequencing has revolutionized the way we classify organisms. And it’s showed us that there is in fact a difference (albeit small) between the members of the genus Mytilus. 

I hope you learned a lot this week! I really enjoyed putting this post together, even though I didn’t cover all the mussels that I wanted to. And I know I promised y'all last week that we would visit the some of the deepest parts of the ocean and we will! Next week will be less lecture and more *let me show you all the pictures of my children that you didn’t ask to see*. Until then, try to be a little less selfish and more shellfish. Cheers, y’all!

[crudlynaturephotos]

[aringamancuso]

Miticoltura nel Delta del Po. #mytilusgalloprovincialis #miticoltura #volgarmentedettecozze #molluschi #bivalvia #mytilidae #deltadelpo (presso Scardovari, Veneto, Italy)

[juniperpublishersoceanography]

Life Aquatic Chemosynthetic in the Photic Zone -Up the Food Chain?- Juniper Publishers

Abstract

Life on Earth has proven highly adaptable, thriving across the most extreme environments, from the highest peaks to the deepest seas, where chemosynthetic microbes (chemoautotrophs) derive energy from inorganic chemical oxidation. In turn, chemoautotrophs are consumed by other organisms and/or have symbiotic associations with other organisms, allowing chemosynthetic energy to percolate up the food chain [1]. For deepwater seeps, this energy is known to ultimately support top predators - fish [2,3]. Here, we argue that chemosynthetic energy also plays a role in photic zone ecosystems, including potentially, an important role in fisheries.

The ecosystem importance of the flow of chemosynthetic energy likely would be enhanced, potentially critically, in nutrient limited environments, such as the deep sea, winter Arctic, or coastal waters when nutrients are for example, sequestered by phytoplankton blooms.

Keywords: Seep; Chemosynthetic; Tropic level; Food chain; Fisheries; Microbes; Bubbles

Introductio

Natural seepage of fluids from geological sources is widespread on land and offshore, the most common fluids being hydrocarbons, particularly methane (CH4) both from petroleum sources and from the microbial degradation of organic matter. Onshore examples include the La Brea tar pits in California [4] and eternal flames [5] at places like Chimera, Turkey and Yanar Dag, Azerbaijan. Offshore examples are reported for water depths ranging from inter-tidal (e.g. San Simón Bay, Galicia, Spain; [6] to >4,000m in the Aleutian Trench [7]) in every sea and ocean [6]. Although CH4 dominates, other compounds, including higher hydrocarbons, also may be present. Some compounds, such as higher alkanes and hydrogen sulfide (H2S) are toxic.

Methane utilization at the seabed

The escape of CH4 from seabed seep sites is limited by anaerobic oxidation of methane (AOM) that occurs close beneath the seabed; Reeburgh [8] suggests that the 'benthic filter' oxidizes as much as 80% of CH4 migrating through seabed sediments. Moreover, the benthic filter is the first step by which chemosynthetic energy enters the food chain, albeit in the seabed in the immediate vicinity of seepage. This microbially- mediated process produces two significant by-products: CH4- derived authigenic carbonate (MDAC), a mineral precipitate that cements the local seabed sediments to form a concrete-like rock, and H2S. MDAC provides a hard substrate that attracts many species, which might otherwise not be found on the 'normal' (non-seep) seabed.

It is well known that deepwater chemosynthetic communities associated with marine hydrocarbon seepage include methanotrophs (which oxidize CH4) and thiotrophs (which oxidize H2S) that, like their hydrothermal equivalents, support localized ecosystems with a high biomass and biodiversity. Associated macrofauna may include species that host chemoautotrophic endosymbionts (siboglinid tube worms, bivalves, sponges, etc.) and predatory and opportunistic feeders such as shrimp, crabs, and fish. The vast majority (to 100% in lower tropic levels) of the energy in such ecosystems derives from non-photic sources. In shallower (<400m) water; however, seep-specialist organisms tend to be out-competed by 'normal' benthic organisms reliant on energy derived from the photic zone i.e., from phototrophs [9], although typical seep species are found for strong shallow seeps [10]. For infaunal species, these oases are density rich relative to the surrounding seabed, although species diversity tends to be relatively reduced [1113]. Species spatial distributions and community composition are correlated closely with chemosynthetic flows [14] and seep- associated substrates [15,16]. Isotopic analysis has identified chemosynthetic energy transfer from chemoautotrophs to nematodes, polychaetes, and other infaunal organisms [17].

Within the immediate vicinity of seeps sediment toxicity impoverishes benthic communities relative to 'normal' seabed [18,19]. However, seep specialists, such as the bivalve Thyasira sarsi and the nematode Astonomena southwardorum (both with endosymbionts) live at North Sea seeps [19]. At the Coal Oil Point seep field, offshore California (and far from a major urban outflow) isotopic studies identifying petroleum energy transfer from chemoautotrophic sulfide oxidizers (Beggiatoa spp.) to nematodes, polychaetes, and other infaunal organisms [17].

Certain polychaete families (Siboglinidae, Capitellidae, and Ampharetidae) and oligochaetes are characteristic of seep sites, some of which benefit from reducing conditions [12]. Sibuet [1] identified five families of bivalves (Vesicomyidae, Mytilidae, Solemyidae, Thyasiridae, and Lucinidae) known to inhabit seep sites; some (at least) of them host methanotrophic and/or thiotrophic symbionts. Bacterial mats, most commonly ascribed to the thiotrophic genus Beggiatoa, are a common (maybe ubiquitous) feature of seep sites at any water depth.

Methane utilization in the water column

Marine seepage is most recognizable as rising bubbles. Bubble plumes are significant for several reasons. Firstly, CH4 is transported up into the water column. Although bubbles at the seabed may be entirely CH4, gases exchange across the bubble surface leading to CH4 loss into the water, enhancing CH4 in the water above seeps relative to 'ambient' seawater [20,21]. Once in the water column, CH4 is subject to methanotrophic bacterial oxidation [22]. This provides another pathway by which chemosynthetic energy enters the food chain as these bacteria are themselves available for predation by higher organisms. CH4 oxidation is not constrained to near the seeps but follows the plume of dissolved CH4-rich water.

Secondly, rising bubbles provide a highly efficient transport mechanism for surface-active materials on the bubble interface ('hitch-hikers’). This transport process shuttles chemoautotrophic microbes up into the water column [23]. Upon bubble dissolution, any surface-attached microbes and other material (organic material, nutrients etc.) are deposited into the water where they become available and attractive to higher tropic level organisms and their predators. Leifer and Judd [24] hypothesized this mechanism as explaining a layer of jellyfish (predators) in an area of North Sea seepage.

Thirdly, bubble plumes entrain surrounding water, generating upwelling flows that transport bottom water and nutrients up into the water column [25]. Pohlman [26] reported that a consequence of this upwelling, and the consequent nutrient enrichment of the upper water column, is increased primary productivity; this seems similar to enhanced productivity associated with other areas of upwelling.

Seepage plumes therefore can be considered beneficial to marine biological productivity because of these features. It has been shown [27,28] that a strong thermocline presents a very real barrier to the upwelling flow, consequently - as also described by Leifer and Judd [24], there tends to be a significant increase in CH4 concentration, and therefore CH4 oxidation and nutrients at and immediately below the thermocline. This creates a layer that would be particularly attractive for higher-level organisms. Such nutrient aggregation could explain reports of significantly increased chlorophyll concentration at the thermocline above on-going seepage from a blow-out site in the North Sea [29].

3 Occurrence of seeps

Marine seepage is widespread, particularly associated with areas of rapid sediment accumulation such as deltas (e.g., the Mississippi, Nile, Niger, East Siberian Sea, etc.), and sedimentary basins, which host petroleum accumulations (the North Sea, Gulf of Mexico, South China Sea, etc.). As pointed out by Judd [30] many of these areas also have highly productive fisheries. We suggest that this is not a coincidence, but relates to the significant advantages provided by seepage, first and foremost by their upwards transport of bio-available chemosynthetic energy and nutrients. Secondly, bubble plumes obscure sonar and sight, protecting against predation. Seepage also is associated with hard seabed substrates that provides habitat.

Bioavailability

Seepage provides a non-seasonally varying source of energy - whereas nutrients and sunlight exhibit strong annual cycles in phytoplankton and zooplankton populations that support the marine food web. Thus, photic zone chemosynthetic energy can provide bridging nutrients for a range of conditions. Specifically, during food-limited time periods, in chronically nutrient-limited areas, on the continental slope below the photic zone (deep sea), during the Arctic winter (night), and for ice-covered waters that block solar insulation. Marine CH4 seepage has been estimated at from 20Tg yr-1 [31] to ~ 50Tg CH4. yr-1 [32] with oil contributing 0.6Gg yr-1 [33], of which a portion is bioavailable. This amounts to a significant contribution to the marine carbon cycle and potentially to the marine ecosystem, particularly for nutrient- limited habitats.

Where nutrient limitation is seasonal, chemosynthetic energy could provide critical bridging support during these seasons and thus support increased diversity. This would be similar to the role watering holes play during the African dry season.

Predation Protection

Seep bubble plumes confuse sonar and sight, protecting against predation. Seep bubble plumes are highly dynamic zones of turbulent upwelling flows that could be highly distracting to predators' the survival strategy of dense fish schools - both visually and by blocking sonar. Seep bubbles also are a locally important noise source that could distract predators.

Interestingly, this very characteristic could make them attractive to cetaceans. The acoustic signature of seeps would be highly audible to cetaceans, serving as acoustic signposts along migration pathways particularly, in basins that support rich fisheries. Additionally, bubble motions could be of interest to intelligent and curious cetaceans, creatures that use bubbles for play and for fishing.

Seepage could explain an energy deficit in cetacean foraging in the Gulf of Mexico (GOM). Based on prey biomass [34], and whale body mass considerations [35] and a tropic level of 4.22 [36], net primary productivity per whale can be calculated. Combined with the conservative NOAA estimated stock [37] of deep-foraging whales (sperm, Gervais', Cuvier's and Kogia) in the Gulf of Mexico suggests ~4x104 metric tons of primary productivity is required (96% from Sperm whales). This is about double the entire GOM open sea (311,000km2) daily phytoplankton primary productivity (2.1x104 metric tons). Chemosynthetic primary production could make up the deficit for these deep foragers.

Recommendation

Given the importance of fisheries to the economy and the need for sustainable management, the hypothesis that seepage supports higher fishery productivity merits investigation. Such research should map the flow of chemosynthetic energy up the food chain in the deep sea and in the photic zone to also better understand their contribution to middle tropic levels. Of interest to fisheries globally, the potential Arctic impacts merit special consideration. In the Arctic, destabilization of submerged permafrost [38] is releasing vast chemosynthetic energy stores - energy that persists through the long dark winter.

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