Deep and Shallow Marine Habitats: Ecology, Biodiversity, and Human Impacts

What is the physical environment of the benthos characterized by?

Very flat and relatively uniform, with exaggerated vertical relief in graphics.

What percentage of the ocean area does the deep sea account for?

60% of ocean area.

What are the stable but extreme conditions found in the deep seafloor?

Stable temperature (2 to 4 ºC), immense pressure (100's-1000's atm), and full-strength seawater salinity.

What is the significance of the pressure in the deep sea?

Pressure increases by 1 atm for every 10 m depth.

What is the typical temperature range below 1000 m in the deep sea?

Constantly between 2 to 4 ºC.

What type of food sources are available in deep benthic habitats?

Detritus from dead plankton, fish, and whales, as well as fecal pellets and marine snow.

What is the organic content of benthic sediment in the abyssal bottom?

Less than 0.25% organic matter.

What is the 'Martin curve' in relation to deep-sea sediment flux?

It describes how flux of organic matter declines exponentially with depth.

How does benthic biomass correlate with surface primary production?

Benthic biomass and growth correlate with detritus from surface primary production, decreasing with depth and distance from shore.

What are the four groups of benthic invertebrates based on size?

Microfauna (<0.1 mm), Meiofauna (0.1-1 mm), Macrofauna (>1 mm), and Megafauna (much larger than 1 mm).

What are the characteristics of echinoderms?

They are exclusively marine, penta-radially symmetrical, have tube feet, and a water vascular system.

What is the most abundant macrofauna in deep benthic habitats?

Polychaetes (segmented worms).

What role do nematodes play in deep-sea ecosystems?

They are important meiofauna that act as detritivores and deposit feeders.

What are the two hypotheses explaining diversity in deep-sea communities?

Area hypothesis (large area promotes speciation) and Time-stability hypothesis (stable environments allow for species accommodation).

What does the species-area relationship imply for marine reserves?

Larger habitats can support more species due to more niches available.

What is the Intermediate Disturbance Hypothesis?

It suggests that small-scale disturbances prevent a few organisms from dominating while allowing others to survive.

What is zonation in the context of rocky shores?

Zonation refers to the distribution of organisms in zones or regions of definite character.

How do tides affect organisms in intertidal habitats?

Tides change water lines, exposure to air, currents, and salinity, impacting the organisms living there.

Why is studying deep benthic habitats important?

They serve as important habitats for algae and invertebrate communities and are model systems for ecological questions.

What is vertical zonation?

The occurrence of dominant species in distinct horizontal bands along the shore.

What are some physical factors affecting vertical zonation?

Wave shock, heat stress, desiccation, gas exchange (dissolved oxygen), and time for feeding as water levels fluctuate.

What biological factors influence vertical zonation?

Competition and predation.

How do most exposed animals cope during low tide?

Many cannot respire; some reduce their metabolic rate, while others, like certain mussels, can respire from air.

What causes vertical zonation in intertidal zones?

Physiological tolerance, settlement of larvae, behavioral responses of juveniles/adults, predation, and competition.

What is the role of competition in rocky habitats?

It can be direct or indirect, with species competing for nutrients or space.

What did Joseph Connell's experiments reveal about barnacle species?

Chthamalus survived better in high intertidal zones due to desiccation resistance, while Semibalanus outcompeted it in lower zones.

What is a keystone predator?

A species whose presence significantly affects community organization, such as Pisaster ochraceus in rocky shore ecosystems.

What happens when Pisaster ochraceus is removed from its habitat?

Mytilus californianus becomes dominant, reducing the abundance of other species.

What factors can structure intertidal communities?

Larval recruitment, disturbances, and the size of patches created by disturbances.

What are the two basic types of benthic habitats?

Soft bottom (organic-rich sediments) and hard bottom.

Why is there often no oxygen below the surface of sediments?

High organic material supply and degradation exceed oxygen diffusion into sediments.

What are some anaerobic metabolisms found in anoxic sediments?

Fermentation, sulfate reduction, and methanogenesis.

What role do benthic invertebrates play in biogeochemical cycles?

They break up detritus and facilitate oxygen penetration into anoxic mud.

What are the classifications of benthic invertebrates based on size?

Microfauna (<0.1 mm), meiofauna (0.1-1 mm), and macrofauna (>1 mm).

What are the two modes of deposit feeding?

Selective feeding (picking individual food particles) and non-selective feeding.

What is the significance of sediment particle size in shallow benthos?

It determines which marine animals thrive; larger particles in fast currents and finer grains in slow currents.

What is the area hypothesis in relation to diversity?

It posits that larger areas can support more species due to greater habitat diversity.

What is the time-stability hypothesis?

It suggests that stable environments allow for greater species diversity over time.

How do disturbances affect competing species in intertidal communities?

They can reduce the abundance of dominant species, allowing coexistence of less competitive species.

What is the role of larval recruitment in community dynamics?

It can strongly affect species composition and dominance, as low recruitment rates can prevent competitively superior species from taking over.

What is bioturbation?

The mixing of sediments by organisms, which allows oxygen-rich waters to penetrate deeper into sediments.

What are the implications of spatial scale in ecological interactions?

Interactions observed at small scales may not apply at larger scales due to differences in patch size and community structure.

What are the two main feeding strategies of benthic invertebrates?

Deposit feeding and suspension feeding.

What is detritus?

Non-living organic material that ranges in food quality from freshly deposited plankton to older detritus.

What do deposit feeders consume?

Both detritus and associated microbes.

How are benthic invertebrates classified?

By taxonomy, size (e.g., meiofauna), location within sediments (epifaunal vs infaunal), and feeding mode.

What role do symbiotic bacteria play in the nutrition of benthic invertebrates?

They provide enzymes to hydrolyze polymers like cellulose, which the animals cannot digest.

What is the function of chemolithotrophic bacteria in benthic ecosystems?

They provide carbon and energy by using inorganic compounds to create organic material from carbon dioxide.

What is the chemical reaction for sulfur oxidation in hydrothermal vent ecosystems?

H2S + CO2 + O2 → organic material.

What are the two types of suspension feeders?

Passive suspension feeders, which go with the flow, and active suspension feeders, which create currents.

How do bivalves like oysters select food particles?

Initially by the gill, then brought to the labial palps for ingestion.

What environmental factors affect life at hydrothermal vents?

Low flows, immense pressure, little to no light, cold temperatures, full-strength salinity, and abundant oxygen.

What is the Martin curve?

A model describing how flux of organic material declines exponentially with depth in the ocean.

What is the typical biomass of deep benthos?

Highly diverse but generally low due to low input of organic material, resembling a desert.

What is the significance of the Alvin submersible?

It was built in 1964 to explore deep-sea environments, including hydrothermal vents.

What are the characteristics of the Lost City hydrothermal vent?

It features metal-poor, high pH water and carbonate towers, differing from typical metal-rich vents.

What is the upper temperature limit for life in hydrothermal vent ecosystems?

Archaea can survive up to 113°C, while the Pompeii worm can withstand 65-85°C.

What is the primary energy source for life at hydrothermal vents?

Sulfide oxidation, which is performed exclusively by bacteria and archaea.

How do chemolithotrophs obtain their carbon?

They utilize inorganic compounds for energy and derive carbon from carbon dioxide.

What happens to organic material as it descends into deeper ocean layers?

Only 1% or less of organic material in the euphotic zone reaches deep sediments.

What is the role of the Tevnia tube worm in hydrothermal vent ecosystems?

It is one of the first colonists of new vent sites and relies on bacteria for nutrition.

What adaptations do adult Pompeii worms have compared to their larvae?

Adults lose their eyes as they settle at hydrothermal vents where vision is unnecessary.

What are chemolithotrophs also known as?

Chemolithoautotrophs, often referred to as chemoautotrophs or chemolithotrophs.

What is the source of carbon for chemolithotrophs?

CO2, making them autotrophs.

What energy source do chemolithotrophs utilize?

They use preformed molecules, classifying them as chemotrophs.

What is the role of H2S in the ecosystem of hydrothermal vents?

H2S is used by chemoautolithotrophic bacteria for energy and CO2 for carbon.

How do hydrothermal vents contribute to the food web?

Chemolithotrophic bacteria are the base of the food web at vents, being fed on by various organisms.

What are hydrothermal vents?

Cracks between continental plates where super-heated seawater releases reduced inorganic compounds.

What is the chemical reaction involving H2S at hydrothermal vents?

H2S + 2 O2 → SO42- + 2 H+.

What is unique about the metabolism of vent life?

It is driven exclusively by bacteria that oxidize sulfide.

What is a characteristic of tubeworms like Riftia pachyptila?

They have no digestive tract, relying on endosymbiotic bacteria for nutrition.

What benefits do vent animals gain from their bacterial symbionts?

They receive food from bacteria and detoxification of H2S.

What do bacterial symbionts gain from vent animals?

A steady diet of H2S and oxygen, along with protection from grazers.

How do photosynthesis and chemoautolithotrophy compare?

Both use the Calvin-Benson cycle for carbon fixation, but differ in energy sources: light vs. chemical energy.

What is the primary source of energy for biological communities at hydrothermal vents?

Hydrogen sulfide from reduced inorganic compounds, rather than light.

How do new hydrothermal vents get colonized?

Through planktonic larvae that swim around and hope to find a suitable site.

What are hyper-thermophiles, and where are they positioned in the Tree of Life?

They are at the base of the Tree of Life, thriving in extreme conditions.

What physical aspects affect midwater organisms?

Temperature, pressure, and light quantity and quality.

What is the temperature range in the midwater environment?

Approximately 18 to 3.5 °C.

How does pressure change with depth in the ocean?

Pressure increases by approximately 1 atm for every 10 meters of depth.

What is the significance of the Lambert-Beer Law in studying light in the ocean?

It describes how light intensity decreases with depth due to absorption and scattering.

What adaptations do midwater organisms have for survival?

Crypsis, bioluminescence, and strategies to maximize energy input while minimizing expenditure.

What is crypsis in midwater organisms?

The ability to blend into the environment, often through color adaptation.

What is bioluminescence and its uses in midwater organisms?

The production of light by organisms, used for avoiding predators, catching prey, and finding mates.

How do midwater animals maximize energy input?

By adopting a predatory lifestyle and consuming a wide variety of prey.

What strategies do midwater organisms use to minimize energy expenditure?

Reducing body density, lowering metabolic rates, and efficient growth.

What is the significance of the DAPI stain in studying deep-sea organisms?

It stains all cells, helping researchers identify and quantify microbial populations.

What is the relationship between biomass and biodiversity in midwater environments?

Biomass is dilute compared to surface waters, but biodiversity remains stable.

What is a key adaptation of midwater organisms to maximize energy input?

They can unhinge their jaws, have longer digestive tracts, and possess distendable stomachs.

What is the significance of hermaphroditism in bathypelagic species?

It helps in reproduction, especially when mates are difficult to find.

What are the general characteristics of midwater animals?

They are slow in metabolism and growth, efficient in vision, opportunistic feeders, and often have flabby bodies with watery tissues.

What defines an estuary?

An estuary is a region where freshwater from rivers mixes with saltwater from the ocean.

How old are the Delaware and other estuaries?

They are approximately 5,000 years old.

What type of estuary is the Delaware River classified as?

The Delaware is classified as a 'drowned river valley' estuary.

What are the salinity units used to measure estuarine salinity?

Salinity is measured in parts per thousand (‰) and practical salinity units (PSU).

What is the typical salinity of the East Coast estuaries?

The typical salinity is around 30 ‰.

What is the net flow direction in most estuaries?

The net flow is generally seaward, with low-density freshwater at the surface and more saline water moving upriver.

What role do estuaries play in marine ecosystems?

Estuaries serve as nurseries for many organisms and have high production and biomass, although they are not very diverse.

What is the life history of the blue crab (Callinectes sapidus)?

Blue crabs spawn in estuaries during summer, with larvae developing on the continental shelf and juveniles using estuaries as nurseries.

How do crab larvae manage to stay in the estuary despite seaward currents?

They position themselves at the surface during flood tides and near the bottom during ebb tides to take advantage of vertical shear in tidal currents.