Oceanography Dr. Jackson
Terms
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- Photostomias guernei
- A deep⬐sea fish with a biological light.
- Biozones – functional divisions
- Euphotic zone extends from surface to where light can still support photosynthesis; to about 100 m ⬢ Disphotic zone extends to about 1000 m and have small but measurable amount of light ⬢ Aphotic zone extend to depths greater than 1000 m where there is no light
- Marine Organism’s Environment
- Density • Viscosity – Physical Support†drag • Salinity – Osmosis • Nutrient • Light • Temperature • Size
- Plankton
- Phytoplanktonplants Zooplanktonanimals Bacterioplanktonmicrobes
- Salinity Effects
- Organisms that have evolved a tolerance for a wide range of salinities are called euryhaline ⬢ Organisms adapted to little salinity change are called stenohaline
- Osmosis
- Passage of water through semipermeable membrane ⬢ Membrane separates to solutions of different solute concentration
- Osmotic Regulation
- When the salinity of an organisms fluid is equal to that of the surrounding ocean water, it is called isotonic ⬢ Hypertonic (saltier) and hypotonic (less salty) organisms experience osmotic pressure ⬢ Adaptations needed to regulate osmotic pressure
- Solar Radiation
- Solar radiation penetrates to greatest depth in the ocean compared with most coastal waters ⬢ However, most highly productive waters are in found in coastal areas, pointing to importance of nutrients
- Temperature Adaptation
- Organisms that can only withstand small temperature changes are called stenothermal and are found in open ocean and at depths ⬢ Organisms that can withstand large temperature changes are called eurythermal and are characteristic of more shallow waters
- Species Distribution on Earth
- Only 17 % of species live in the ocean ⬢ Most species live in the benthos ⬢ Uniform conditions of the open ocean do not force organisms to adapt, change ⬢ Although fewer species, ocean is more varied.
- Benthic vs planktonic plants
- Benthic plants are attached to the bottom. 􀂄 Mostly large plants (macrophytes) 􀂄 Marine plants do not stand up to the waves and currents but bend. Planktonic plants are freely floating plants 􀂄 Mostly single celled (phytoplankton or microphytes) 􀂄 Drift with the currents
- Seagrasses
- The roots and horizontal stems (rhizomes), often buried in sand or mud, anchor the grasses and absorb nutrients. 􀂄 Leaves, usually green, are produced on vertical branches and also absorb nutrients.
- What is primary productivity?
- 􀂄Primary productivity is the rate at which energy is stored by organisms through the formation of organic matter (carbon compounds). 􀂄The energy comes from solar radiation (photosynthesis) or chemical reactions (chemosynthesis). 􀂄99.9 % of the ocean’s biomass get their carbon directly or indirectly from photosynthesis. 􀂄Except that produced by chemosynthetic organisms; such as those around hydrothermal vents and deep-sea archaea that oxidize hydrogen sulfide and methane to synthesize food.
- Biological productivity
- 􀂄Primary producers are those organisms that photosynthesize their own food from water, carbon dioxide and the energy of solar radiation. 􀂄Photosynthetic primary producers include marine plants, macroalgae (seaweed), bacteria and microalgae (microscopic algae). 􀂄Most inorganic carbon is fixed by phytoplankton; microscopic algae and bacteria floating around in sunlit surface waters.
- What do we measure?
- Measure for a “short†time, so that do not worry about system changing during the measurement. 􀂄 If we want to know how much plant production is feeding the rest of the system, need to account for plant respiration.
- How do we express it?
- Want to standardize on a unit area (m2). 􀂉 Would like to be able to see how efficiently plants are using light, which we measure per unit area. 􀂉 Would like to make a “fair†comparison between Galveston Bay and Gulf of Mexico to see which is running faster, without worrying about the fact that the GoM is much bigger.
- Types of photosynthetic productivity:
- 􀂄Gross primary production – rateof organic carbon produced by photosynthesis. Usually expressed either as a mass per unit area per time ( e.g., g C m-2 d-1) or chlorophyll per unit volume (mg m-3 d-1 or μg L-1 d-1). 􀂄Net primary production – what remains after the photosynthetic organism has satisfied its needs in terms of cell maintenance through respiration. 􀂄Net primary production is gross primary production minus cellular respiration and is manifested as growth, reproduction, release of dissolved organic compounds.
- Measuring primary production: start by measuring plant biomass.
- 􀂄Plankton nets can be used to sample the plankton. Tells us what is present, not how fast they are growing. 􀂄Phytoplankton biomass can be estimated by using chlorophyll (green pigment used in photosynthesis) by capturing phytoplankton on filters and measuring the amount of chlorophyll captured. 􀂄Phytoplankton biomass is also measured using satellite instruments to measure ocean color, which is strongly affected by the presence of chlorophyll containing phytoplankton.
- Measuring productivity
- Rates of productivity can be estimated by measuring photosynthesis rates and respiration rates. 􀂄Photosynthesis rates usually measured by the production of oxygen or the assimilation of inorganic carbon into organic carbon. 􀂄Oxygen production (photosynthesis) and uptake (respiration) can be measured by enclosing samples of seawater in bottles and measuring the change in oxygen concentration in the bottles.
- Oxygen Method
- Gross primary production is the total amount of organic matter produced per unit of time 􀂄 Net primary production is what is left after respiration 􀂄 Change in oxygen 􀂉 Light bottle: photo-resp 􀂉 Dark bottle: -resp
- Divide gross primary production into two components:
- 􀂄New production – generated using nutrients brought in from outside the local ecosystem by processes such as upwelling. 􀂄Regenerated production – generated using nutrients that are recycled within the system. 􀂄As the ratio of new production to gross primary production increases, so does the ecosystems ability to support animal populations. 􀂄Explains why upwelling areas, such as the in the coastal water off Peru (chapter 7) are such valuable fishing grounds. 􀂄New production – generated using nutrients brought in from outside the local ecosystem by processes such as upwelling. 􀂄Regenerated production – generated using nutrients that are recycled within the system. 􀂄As the ratio of new production to gross primary production increases, so does the ecosystems ability to support animal populations. 􀂄Explains why upwelling areas, such as the in the coastal water off Peru (chapter 7) are such valuable fishing grounds.
- Light transmission in ocean waters
- 􀂄Ocean selectively absorbs visible light of the longer wavelengths (red, orange and yellow). 􀂄Red light usually absorbed within the upper 10 m of ocean. 􀂄Yellow absorbed by about 100 m. 􀂄Shorter wavelengths (e.g. blue) penetrates the ocean to a greater depth.
- Photosynthetic organisms – microscopic algae
- Most microscopic algae are phytoplankton. 􀂄Produce food directly or indirectly for 99 % of marine animals. 􀂄Diatoms – important primary producers, cells contained within a test of silica. 􀂄Coccolithophores – covered in small calcareous plates called coccoliths. 􀂄Dinoflagellates – use flagella for locomotion, therefore have a slight capacity to move themselves into more favorable light and nutrient conditions. Sometimes exist in great abundance and color the water, producing a red tide, which is more accurately termed a harmful algal bloom (HAB). 􀂄Dinoflagellates are associated with various types of food poisoning, including ciguatera, caused by eating tropical reef fish which contain high levels of naturally occurring dinoflagellate toxins.
- Biotic Community
- Assemblage of organisms that live together within some definable area 􀀩 Ecosystem = biotic community + environment
- Ecosystem
- Producers - algae and some bacteria 􀀩 Consumers - heterotrophs 􀀩Decomposers - heterotrophs (mainly bacteria, some fungi)
- Consumers
- 􀀩 Herbivores 􀀩 Carnivores 􀀩 Omnivores 􀀩 Bacteriovores
- Symbiosis
- 􀀩 Two or more organisms closely associated such that at least one or more benefits from this association 􀀩 Corals – Animal feeding on particles – Algae photosynthesizing 􀀩 Green sea anemones at shore line
- Types of Symbiosis
- 􀀩Commensalism - smaller or less dominant participant benefits without harming its host 􀀩 Mutualism - both participants benefit 􀀩 Parasitism - the parasite benefits at the expense of its host 􀀩 Mutualism extremely common among marine organisms (tending a garden)
- Energy Through Trophic Levels
- Energy flow is unidirectional 􀀩 Ultimately, energy goes to heat 􀀩 As biomass moves through the food chain, there are losses such that a small percentage ultimately reaches the highest trophic levels
- Biogeochemical Cycle
- 􀀩 Inorganic nutrient is used to make organic matter by autotroph – Photo-autotroph- use light energy to make organic matter – Chemo-autotroph- use chemical energy to make organic matter (eg, bacteria that use sulfide as energy source, use) 􀀩 Heterotrophs require organic matter to grow
- Trophic transfer in the sea
- Animals tend to feed on food 10% of their size 􀀩 For food to get to a size we can eat, it might go through 4-5 steps. 􀀩 If four steps, we get 0.1 x 0.1 x 0.1 x 0.1= 10-4=0.0001 of original food 􀀩 The closer we eat to the original plant, the more energy efficient.
- Marine Productivity
- Plant growth fuels the growth of all animals 􀀩 Plant growth in the ocean usually limited by either insufficient light or low nutrient concentrations (N, P) 􀀩 Nutrients are stripped out of the surface water by plant growth, settling to deeper water 􀀩 Result is low surface nutrient concentration at surface
- Marine productivity-2
- Growth requires the movement of nutrients to the surface 􀂋Gentle, slow mixing 􀂋Upwelling 􀂋Winter mixing 􀀩 Runoff from the land can also add nutrients, support plant growth
- Gulf of Mexico- interlude
- Highest productivity next to coast 􀀩Mississippi River is a big provider of nutrients, affects Texas shelf to Mexico 􀀩 Center of Gulf can be quite sterile 􀀩 Highest biomass in winter, when weather increases mixing 􀀩 Can see effect of Loop Current on central Gulf
- Fundamental constraints
- Animals feed by capturing other particles (phytoplankton, animals, detritus) ⬢ Size of feeder/size of food ~ 10 ⬢ Big things are rarer. Need to be able to search larger volumes of water. ⬢ Will be true for benthic as well as planktonic animals.
- Benthic Animals
- • 98 % of ocean animals live on the ocean floor • The majority of benthic species are found on the continental shelf • Must adapt to: – conditions in overlying seawater – conditions in sediments – pressure from other organisms
- Needs for life in the benthos: food
- Photosynthesis†confined to shallow regions next to coast (seaweeds) • Particles falling from overlying water – Directly†grab from water (suspension feeding) – Indirectly†eat what falls to bottom – Problem: most eaten on the way to the bottom • Eat someone else • Oxidize chemicals (microbes/chemoautotrophs)
- Needs for life in the benthos: home
- Need to be able to hold on when water flows. – Attach to surface, particularly in intertidal • Needs to be hard rock, else float away – Burrow into sand • All the time†can be harsh chemically (no oxygen) • When conditions get bad • As anchor (e.g., sea pen) • Live in a tranquil environment (deep sea)
- High Intertidal
- The upper intertidal zone has the widest range of heat and cold. desiccation in the summer, freezing in the winter. ⬢ Fresh water, both surface water from rainfall and subsurface flow, can impact populations. ⬢ With limited inundation time, marine food resources are limited. ⬢ Mostly scavengers, which rely on "islands" of wrack material for sustenance.
- Mid Zone
- The mid⬐littoral zone is characterized by a moderate inundation time, but is subject to many of the same rigors as the upper zone (temperature extremes, fresh water). ⬢ The mid zone is more subject to rapid sediment removal during winter storms, requiring extreme mobility of its fauna.
- Mid⬐Intertidal
- The mid⬐intertidal zone is exposed to air briefly once or twice a day ⬢ At wave⬐exposed sites, the mussel, Mytilus, can dominate the available attachment substratum. ⬢ Also starfish.
- Low Intertidal Zone
- The low intertidal zone, extending into the shallow subtidal, is almost fully marine, being aerially exposed for short periods only on the lowest tides. ⬢ The low intertidal is subject to almost constant wave action, requiring that the inhabitants be either rapid burrowers (e.g. Blepharipoda) or protected against mechanical damage (e.g. Tivella). ⬢ It houses the most diverse faunal assemblage of the beach zones.