Sedimentation n Sediment distributions are controlled by production (silica) and dissolution (carbonate) n Therefore, in order to understand the distribution of siliceous sediments, we’ll need to understand: n General marine productivity n Global patterns of productivity n Biological productivity of upwelling water n We’ll start with a review of productivity n general n limiting factors

Productivity n All ecosystems operate day to day by exchanging energy and matter. n Plants convert energy from the sun into organic matter which in turn may be consumed by grazers or decomposed by bacteria and fungi. n The pathways of energy flow can be depicted by a flow diagram. This is a simple diagram…..

This is review, but it’s an important concept. Food Webs and Trophic Dynamics (Cont.) n Solar energy provides the power for ecosystems. Plants use chlorophyll to capture the sun’s energy. n Photosynthesis is the process whereby plants capture light energy and convert it into chemical energy in the form of organic molecules.

Productivity n All of this takes place both on land and in the oceans n In the oceans, it looks like this:

Marine Productivity (Cont.) n Now let’s consider some of the factors which limit production n We can try to predict which places in the ocean will be productive based on our in-depth knowledge of the oceans’ physics and chemistry

Marine Productivity ( Factors limiting primary productivity,Cont.) n Phytoplankton need 116 times more carbon than phosphorus, and 16 times more nitrogen than phosphorus. n Since carbon is plentiful in the ocean as CO 2 (actually HCO 3 - ), the amount of nitrogen and phosphorus present usually regulate plant production.

General Marine Productivity (Cont.) Equatorial upwelling arises due to wind and the Coriolis effect.

Equatorial Upwelling n Caused by: n Coriolis acceleration n offset of solar and geographic equators n Ask Dimitri for details

. Upwelling n Coastal upwelling occurs along the eastern edges of ocean basins when prevailing winds blow parallel to the land

Upwelling n Coastal upwelling occurs in these places n has substantial impact on productivity and economy

Biological Productivity of Upwelling Water (Cont.) n One of the most well studied upwelling regions is offshore Peru in western South America.

Global Patterns of Productivity n When nutrients and light are abundant, plants in the ocean (e.g. diatoms) will grow rapidly by simple cell division and form a bloom with cell concentrations exceeding 10 6 /liter. n Blooms may discolor the water because of pigments in the cells.

Global Patterns of Productivity

n Global abundance patterns of benthic animals also mimic primary productivity patterns n These animals ultimately rely on organic matter from the photic zone.

Deep-sea Sedimentation (Cont.) From all this, we can understand the distribution of sediments

Seafloor Features n Scales vary from small to large n Processes of formation are similar n Currents: all depths n Waves: shallow only

Seafloor Features n On a smaller scale, the effects of currents are less obvious but still distinct. n From underwater photographs,we can discern the long-term flow patterns

Seafloor Features n The development of moats applies to large and small objects: n Worm tubes n islands

n Ripples are formed by steady or oscillatory flow n Exact morphology is a complex function of flow, turbulence and sediment grain size

n Sediment waves are large scale features n Formed by slow, steady flow over long time periods n Good analogy with wind waves on sea surface n May dominate local topography in the deep sea

Seafloor Features n Where the flow patterns and topgraphic patterns allow, sediment can be eroded

Seafloor Features n Drifts are the largest transportational features n Indicate flow patterns n Controlled by flow and topography