The Open Ocean and Deep Floor

• Plankton are the organisms which float in the water and have no ability to propel themselves against a current.

• They can be divided into phytoplankton (plants) and zooplankton (animals).

• Nekton are active swimmers and include marine fish, reptiles, mammals, birds and others.

• Benthos are the organisms which live on the bottom (epifauna) or within the bottom sediments (infauna).

• Some organisms cross from one lifestyle to another during their life, for example being planktonic early in life and benthonic later.

9-3Classification of Lifestyle

Inhabitants of Pelagic Environment

> 5000 species

Holoplankton are organisms that are planktonic for their entire life cycle.

Examples of holoplankton include diatoms, radiolarians, dinoflagellates, foraminifera, amphipods, krill, copepods, salps, and jellyfish.

Meroplankton organisms that are planktonic for only a part of their life cycles, usually the larval stage.

Examples of meroplankton include the larvae of sea urchins, starfish, crustaceans, marine worms, and most fish.

NektonExamples are adult krill, small fish, whales, and tuna

Inhabitants of EpiPelagic or Photic Zone

Most animals are found there, yet 10% ocean volume

Environment: Light, Well Mixed, Nutrients

Food Source: primary production from Phytoplnakton

Adaptation: highly variable dependent on oceanic region

Inhabitants of EpiPelagic or Photic Zone

Each Epipelagic zone is characterized by T and S associated with ocean circulation environment.

Example ofKrill Distribution

Krill Distribution Patterns (in the Epipelagic Zone)

Inhabitants of MesoPelagic

Environment: Dim Light

Food Source: Animals relay on primary production from Photic Zone

Adaptation: Mesopelagic fishes seldom exceed 10 cm in length, and many are equipped with well-developed teeth, large mouths, highly sensitive eyes, and photophores.

• Some mesopelagic fishes: (a) loosejaw, Aristostomias; (b) spookfish, Opistoproctus; and (c) hatchetfish, Argyropelecus. All are 5-20 cm in length.

Inhabitants of MesoPelagic

Inhabitants of BathyoPelagic

Environment: NO Light

Food Source: Small animals/fish from mesopelagicMostly Prey-Predator Environment

Adaptation: Bathypelagic fishes seldom exceed 10 cm in length, and many are equipped with well-developed teeth, large mouths, highly sensitive eyes,

and photophores (only source of ligth).

A few fish of the deep sea, shown at their typical depths. Most have reduced bodies, large mouths, and lures to attract prey.

4000 m

1000 m

Inhabitants of Pelagic Zone At different depths

Adaptation Strategies in Pelagic Zone

Physical/Morphological:

Body shape and locomotion Buoyancy regulationsEcholocationmore...

Behavioral:

Vertical migration and feeding techniqueSchooling Migration patternsmore…

Adaptation Strategies in Pelagic ZoneBody shape and different types of locomotion

Power and glide strokes of three pectoral-swimming tetrapods.

Adaptation Strategies in Pelagic ZoneBody shape and speed

Streamlined body forms of two swift pelagic animals: (a) bottle-nosedolphin, Tursiops; (b) tuna, Thunnus.

Adaptation Strategies in Pelagic ZoneBuoyancy regulation

• The development and relative positions of physostomous and physoclistous swim bladders.

Swim Bladder

Adaptation Strategies in Pelagic ZoneEcholocation a way of sensing. The animals emit high-pitched clicks and sense them as they bounce back off objects (like prey)

Cutaway view of the complex structure of a sperm whale head.

Adaptation Strategies in Pelagic ZoneFeeding Strategies, feeding currents

A generalized kite diagram of net collections of adult female copepods, Calanus finmarchicus, during a complete one-day vertical migration cycle.

Adaptation Strategies in Pelagic ZoneFeeding Strategies, vertical migration

Daily or seasonal changes in light intensity seem to be the most likely stimulus for vertical migrations.

Feeding on Dispersed Prey

The appendicularian Oikopleura, within its mucous bubble. Arrows indicate path of water flow.

Adaptation Strategies in Pelagic ZoneFeeding Strategies, selective size

Adaptation Strategies in Pelagic ZoneSchooling

• Protection

• As a means of reducing drag while swimming

• To keep reproductively active members of a population together.

Adaptation Strategies in Pelagic ZoneMigrations

– Larger and faster nekton participate in regular and directed migrations that serve to integrate the reproductive cycles of adults into local and seasonal variations in patterns of primary productivity.

Migratory patterns of the Bristol Bay sockeye salmon (top) and the east Pacific skipjack tuna (below). Adapted from Royce et al 1968, and Williams 1972.

they follow ocean currents

Adaptation Strategies in Pelagic ZoneMigrations

Geographical distribution of male and female elephant seals during post-molt (left) and post-breeding migrations. Adapted from Stewart and DeLong, 1993.

Elephant Seals

Inhabitants of DEEP Sea Floor – Benthic Environments

Dominant Species:echinoderms, polychaete worms, pycnogonids, and isopod and amphipod crustaceans become abundant. Mollusks and Sea stars decline in number.

Environment: High pressure, cold, lower dissolved oxygen (5 ppm), bioluminescence, slow currents, lots of sediments.

Food Source: mostly detritus + oxygen from above (respiration)

Adaptation: highly variable

Seafloor images showing the deposition of phytodetritus before (a) and 2 months after (b) a phytoplankton bloom in the photic zone above (Courtesy of R. Lampitt).

Most benthic animals in the deep sea are infaunal deposit feeders, extracting nourishment from the sediment in much the same manner as earthworms.

In July 2002, an unprecedented low oxygen or hypoxic zone developed off thecentral Oregon coast. The zone was extensive in size, at least 820 km2 andresulted in widespread die-offs of marine fish and invertebrates. Researchindicates that this hypoxia can be linked to larger-scale, anomalous changes inocean circulation over the Eastern North Pacific in 2002. (June 17,2004, Nature429: 749-754).

In June 2004, researchers at OSU1 again recorded dissolved oxygen valuesover the central Oregon shelf that were below the hypoxia threshold of 1.43 ml l-

Recurring Hypoxia off Oregon Coast

Environment: High pressure, cold, lower dissolved oxygen (5 ppm), bioluminescence, slow currents, lots of sediments.

and the discovery of new ecosystems

HydrothermalVents

Hydrothermal vent communities (red dots) and cold seeps (blue dots).

• Hydrothermal Vent Communities– Dissolved H2S emerging from seafloor

cracks is used as an energy source by chemosynthetic bacteria

– These bacteria become the source of nutrition for dense populations of the unique animals clustered around these springs.

Comparison of primary production in phothsynthetic and chemosynthetic systems.

• Hydrothermal Vent Communities

External appearance (a) and internal anatomy (b) of the tubeworm, Riftia.

(a) (b)

• Cold-Seep Communities– Densely populated animal communities

dependent on chemosynthetic bacteria, include

• cold-water brine seeps• methane seeps• earthquake-disturbed sediments of deep-sea fans