Nekton in Marine Ecosystems

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Questions and Answers

Which of the following marine reptiles is known for modifying its limbs into paddles for swimming?

Sea snakes

All marine reptiles

Leatherback turtles (correct)

Green turtles (correct)

What defines the habitat of meroepipelagic fishes?

They spend only part of their life in the epipelagic region and visit it for prey. (correct)

They are only found in freshwater regions.

They remain exclusively in the epipelagic region.

They thrive only in deep ocean environments.

What is a key characteristic of seabirds in terms of reproduction?

They have a high adult survival rate. (correct)

They have a short reproductive cycle.

They reproduce multiple times a year.

They do not care for their young.

Which group of marine life primarily includes seals, dugongs, and dolphins?

Mammals Signup and view all the answers

What type of diet do the carnivorous turtles primarily consist of?

Fish and cephalopods Signup and view all the answers

Where do most seabirds typically breed?

Shorelines and coastal regions Signup and view all the answers

What is a notable feature of the blue sulphur-bottom whale?

It grows up to 25 meters in length and weighs 60-80 tons. Signup and view all the answers

Which type of marine life is primarily known for its ability to swim fast and drift motionless?

Reptiles Signup and view all the answers

What is the primary feeding mechanism employed by sessile epifauna?

Filter feeding using currents Signup and view all the answers

What type of shell morphology adaptations do some gastropods exhibit to avoid sinking into soft sediments?

Bulbous shapes with broad bases Signup and view all the answers

Which of the following organisms is classified as a sessile epifauna?

Barnacles Signup and view all the answers

How do some gastropods contribute to sediment volume?

By digesting nutrient material and excreting pellets Signup and view all the answers

What type of locomotion do echinoderms primarily utilize?

Crawling using sucker feet Signup and view all the answers

Which statement accurately describes the mobility of sand dollars?

They move slowly by using whisker-like feet. Signup and view all the answers

How do some brachiopods anchor themselves to hard substrates?

Using a stem-like foot that extends from the hinge line Signup and view all the answers

What describes the general body shape of echinoderms like sea urchins and starfish?

Bulky and spiky Signup and view all the answers

Which organisms are primarily classified as sediment destabilizers?

Organisms that graze or plow through sediment Signup and view all the answers

What type of feeding behavior do meiofaunal organisms, like nematodes, exhibit?

Detritus feeders consuming decaying material Signup and view all the answers

How do clams infaunal organisms filter food from their environment?

Through their gills using siphons for water circulation Signup and view all the answers

Which sediment type is known to support a greater biomass of meiofaunal organisms?

Mud sediment Signup and view all the answers

What physical characteristic do sea urchins possess that aids in their feeding behavior?

Short, stubby spines Signup and view all the answers

Which organisms are considered significant food sources for macrofaunal deposit feeders?

Meiofaunal organisms like nematodes Signup and view all the answers

Which of the following statements about infaunal organisms is true?

They typically move only when disturbed from their burrows. Signup and view all the answers

Which invertebrate phylum does not fall under meiofaunal organisms?

Mollusca Signup and view all the answers

What causes density currents in ocean waters?

Heating action of the sun on ocean water Signup and view all the answers

Which current type is primarily affected by the gravitational pull of celestial bodies?

Tidal currents Signup and view all the answers

What is the role of dissolved oxygen in marine ecosystems?

It is utilized by animals with gills for respiration. Signup and view all the answers

How do dissolved nutrients like nitrogen, phosphorous, and potassium primarily enter marine environments?

From animal waste and decomposition Signup and view all the answers

Which factor does NOT significantly influence the concentration of dissolved gases in seawater?

The depth of the ocean Signup and view all the answers

Which of the following statements is true about oxygen levels in marine environments?

High amounts of marine animals lead to low oxygen levels. Signup and view all the answers

What is a primary function of ocean currents in relation to planktonic larvae?

Currents help distribute them to different parts of the ocean Signup and view all the answers

What primarily determines the levels of dissolved oxygen in marine water masses?

The proportion of plants and animals present Signup and view all the answers

What defines the compensation depth in aquatic systems?

The depth at which 1% of the incident radiation penetrates Signup and view all the answers

How does temperature generally affect the rate of photosynthesis?

It increases with temperature until a certain point Signup and view all the answers

What role do nutrients, specifically phosphates and nitrates, play in primary production?

They are absorbed during photosynthesis, limiting further production Signup and view all the answers

What can affect the compensation depth in aquatic environments?

Geographical variations and seasonal changes Signup and view all the answers

Under what conditions may compensation depth be absent?

During winter months at high latitudes Signup and view all the answers

What is the main influence of salinity on primary production in the ocean?

It generally has little effect due to minimal salinity variation in open oceans Signup and view all the answers

Which phytoplankton species has an optimum photosynthesis rate at specific salinities?

Skeletonema Signup and view all the answers

What indirect effect does temperature have on primary production?

It influences the mixing of water, leading to nutrient supply Signup and view all the answers

Study Notes

Nekton

Meroepipelagic fishes spend part of their lives in the epipelagic region to hunt prey
Herbivorous fish like anchovies play an important role in upwelling areas, supporting large fish populations
Nektonic marine reptiles include sea snakes and turtles
Sea turtles are true pelagic animals often visiting shores for breeding
Sea turtles have paddle-like limbs for fast swimming and can drift motionless
Leathery turtles and hawksbill turtles are carnivores, feeding on invertebrates and fish
Green turtles feed mainly on seaweeds and eelgrass
Sea snakes are viviparous and venomous, with over 60 species found in the Indo-Pacific region
Seabirds are warm-blooded nektonic animals playing a significant role in the marine food chain
Seabirds are not strictly defined and cover birds that obtain food from the sea
Seabirds typically breed on offshore or coastal areas, including cliffs, dunes, skerries, and islands
There are 274 species of seabirds including penguins, albatrosses, fulmars, petrels, shearwaters, pelicans, cormorants, and skuas
Seabirds are characterized by long lifespans, late maturity, slow reproduction, and intense parental care
Marine mammals include seals, dugongs, manatees, dolphins, porpoises, and whales, with whales being the most important
Whales are the largest members of nekton, with the blue whale reaching 25 meters in length and weighing 60-80 tons

Benthos

Some benthic organisms have thick, heavy shells for protection
Some benthic organisms have adaptations to prevent sinking into soft sediment, like spines
Echinoderms, including sea urchins, sea cucumbers, and starfish, have numerous appendages for movement
Sea urchins live on hard substrates feeding on debris or live on unconsolidated sediment
Sand dollars have limited mobility but can move slowly using whisker-like feet
Sessile epifauna are attached to substrates and have no mobility
Sessile epifauna include both solitary and colonial organisms
All sessile epifauna are filter feeders relying on currents for food
Sessile invertebrates on hard substrates include barnacles, oysters, some brachiopods, mussels, sponges, sea anemones, and sea lilies
Brachiopods and mussels are bivalves and filter feeders
Some benthic organisms move through sediment (sediment destabilizers)
Some benthic organisms construct burrows and move within them (sediment stabilizers)
Benthic organisms near the surface may be displaced by waves, currents, or other organisms
Grazing or plowing organisms include sea urchins, snails, and clams
These organisms have streamlined shells and ingest large quantities of sediment, extracting organic debris and excreting sediment pellets.
Some benthic organisms have great burrowing abilities, like ghost shrimp, which can be found over 2 meters beneath the substrate
Numerous clams burrow near the surface for feeding and use inhalant and exhalant siphons to circulate water through their digestive systems
Many types of worms also occupy this mode of life
Infaunal organisms typically only move when dislodged from their burrow
Meiofaunal organisms include a range of invertebrate phyla and are abundant in intertidal beaches
The most common meiofaunal groups are nematodes and harpacticoid copepods
Meiofauna are an important food source for larger organisms like polychaetes, holothurids, and fish
The amount of meiofaunal biomass varies depending on the type of sediment, with mud harboring more than sand
Meiofaunal organisms exhibit a variety of feeding habits, including herbivory, detritivory, suspension feeding, and predation

Ocean Processes

From the equator, water moves towards the poles, becoming cooler and denser
Oxygen depletion or stagnation is rare in the oceans due to circulation
Currents transport food, remove waste, distribute larvae, and break temperature barriers
Density currents are caused by the heating action of the sun, warm water rises and spreads, cold water sinks and spreads
Tidal currents are caused by the gravitational pull of the moon and sun on ocean water
Wind currents are caused by wind blowing on the water surface
Wind currents only affect surface waters
Dissolved oxygen is essential for respiration in marine animals, and is replenished through photosynthesis by plants and diffusion from the surface
Dissolved carbon dioxide is used by marine plants for photosynthesis
The amount of dissolved gases varies depending on the types and abundance of life forms present
Nutrients like nitrogen, phosphorous, and potassium are important for plant growth
Nutrient levels increase from animal feces and decomposition
The rate of photosynthesis declines as light intensity decreases, reaching a compensation depth where photosynthetic rate equals respiration rate
Compensation depth is the depth where 1% of incident radiation penetrates and marks the lower limit of the euphotic zone
Compensation depth varies geographically and seasonally
Temperature influences photosynthetic production, with rates generally increasing with temperature until a point is reached
Each species of phytoplankton is adapted to a particular temperature
Temperature indirectly influences photosynthetic production by influencing thermocline formation and water mixing
Salinity can influence primary production, with some species showing optimal growth at specific salinity ranges
Salinity generally has less influence on overall oceanic productivity due to limited variation in the open ocean
Nutrients like phosphate and nitrate are major limiting factors for primary production in aquatic systems
Phytoplankton absorb nutrients during photosynthesis, decreasing nutrient concentration in the euphotic zone and limiting further production
Bacteria regenerate some nutrients utilized by phytoplankton within the euphotic zone

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Description

Explore the diverse world of nekton, including marine reptiles, herbivorous and carnivorous fish, and seabirds. Learn about their roles in the marine food chain and how they adapt to their pelagic lifestyles. This quiz covers the significance of these creatures in marine ecosystems.