Life in the Ocean All living things grow, metabolize, react to the external environment and reproduce –Organisms need energy and ingredients Energy: the ability to do work –Metabolism: process by which organisms gain energy from the external environment. The ingredients: Biomolecules –Carbohydrates, Proteins, Lipids, Nucleic Acids
Photosynthesis and Respiration
Nutrients Materials needed to make biomolecules. –Raw materials are nutrients, and they include minerals, vitamins, and other inorganic compounds Nitrogen and Phosphorus are usually the most important nutrients in the marine environment. Often called limiting nutrients because without them they limit productivity. –Nitrate (NO3 -1 ), the most important form of nitrogen, is used in making proteins and nucleic acids – Phosphate (PO4 -3 ), the most important form of phosphorus, is used in making phospholipids, ATP and DNA.
Primary Production Sugars produced by photosynthesis are raw material for the other organic compounds, such as lipids, proteins and nucleic acids. –When autotrophs produce more organic matter than they use, there is an overall gain in organic matter. –This net increase is called primary production, and it is this primary production that supplies all the heterotrophs, i.e. animals, with food.
Challenges of Life in the Ocean Lack of substrate –They are at constant risk of sinking –They are constantly being thrashed around by mixing.
Challenges of Life in the Ocean Transparency of seawater –Adequate light for photosynthesis only exists in the upper part of the ocean, in a region known as the euphotic zone, ranges from m in depth. The euphotic depth is the depth at which light levels are 1% of surface light, which is considered to be when light becomes limiting for photosynthesis.
Challenges of Life in the Ocean Lack of Nutrients –Most of the nutrients in the ocean are below the euphotic zone. Where there is enough light, there often aren’t enough nutrients for primary production
Temp, O 2, Nitrate Profiles
Global Nitrate Profiles
Global Primary Productivity
Phytoplankton Phytoplankton (plant-wanderer) are the primary producers in the open ocean –They range in size from m (there are 1000 m in a mm) –The smaller you are, the less you sink. –When you are that small, you can be thrown around by breaking waves and it doesn’t affect you at all. –When you’re that small you have a higher surface-to-volume (S/V) ratio, which increases your ability to pick up nutrients, which may be in very low concentrations. »The larger the organism, the smaller the S/V ratio, the smaller the organism, the larger the S/V ratio. –Being that small you tend to reproduce quickly, so that your numbers can increase rapidly under the right circumstances. »During a phytoplankton bloom, some cells will divide as much as 3 times per day.
It’s Good to be Small The smaller you are, the less you sink. When you are that small, you can be thrown around by breaking waves and it doesn’t affect you at all. When you’re that small you have a higher surface-to-volume (S/V) ratio, which increases your ability to pick up nutrients, which may be in very low concentrations.
Phytoplankton Reproduce Exponentially Being that small you tend to reproduce quickly, so that your numbers can increase rapidly under the right circumstances. –During a phytoplankton bloom, some cells will divide as much as 3 times per day.
Plankton Greek for Wanderer or Drifter Organisms that can’t swim against a current Usually small –Picoplankton: μm –Netplankton: >20 μm Types –Phytoplankton –Zooplankton –Protists
Phytoplankton Greek for Plant Drifter Vary in size from μm Grow very fast –Cells divide as much as 3 times/day Make own food but need –Light, Nitrogen, Phosphorus Examples –Diatoms, Dinoflagellates
Dinoflagellates
Diatoms
Zooplankton Animal Wanderer Holoplankton: plankton their entire lives –Ex: Copepods Meroplankton: planktonic part of their lives –Ex: Fish, crabs, lobster, barnacles Need to eat other things Examples –Copepods, Protozoans, Pteropods, Jellies
Copepods
Protozoans
Pteropods
Jellies