THE SEA FLOOR

Methods of bathymetry

Features of the Ocean Floor Drain The Ocean

How do geologic features get there?

Seamounts: Extinct undersea volcanoes Mid-ocean ridge: plates splitting

Linear arrangement of seamounts suggests they may originate as a result of plate movement over a hot spot

If seamounts can rise above sea level for two reasons 1. buildup of material in a cone 2. upwelling of hot mantle pushes plate upward. Above sea level they are subject to processes that flatten them 1. wave erosion 2. colonization by reefs Later, the island sinks (subsidence) and/or sea level rises drowning the flat-topped seamounts called GUYOTS. Formation of Guyots

Submarine canyons are major transporters of sediment from the continent to the deep ocean floor.

Seafloor organisms

We are the Benthos The community of organisms that live on, in, or near the seabed (the benthic zone)

Benthic organisms live ON or IN the bottom Epifauna: Benthic animals that live ON the surface of the sea bottom (sponges, sea squirts) Infauna: Benthic animals that live IN the sea bottom (clams, worms) Hear “Benthos” think Bottom

2 Major Groups of Benthic Organisms 1. Filter Feeders: Draw food out of the water (e.g. quahogs!) 2. Deposit Feeders: Ingest sediment and filter organic matter within it (e.g. mud snails)

epifauna or infauna?

Which sediment profile would you rather live in? Light color indicates oxygenated substrate. Dark color indicates anoxic sediment.

Most benthic creatures cannot move very far, if at all, so they can’t avoid pollution or unhealthy water conditions. Benthic communities are exposed to many stressors, including * chemical contaminants *excess sediment *low oxygen levels

Many chemical contaminants bind to bottom sediments, remaining there for years. Benthic species become contaminated when they feed and live in these toxic sediments.

How would excess sediment affect photosynthetic organisms? Sessile animals?

Excess sediment also impacts anadromous species salmon preparing redd What factors would degrade salmon redd-building environment?

In summer, high temperatures and nutrient pollution often lead to low-oxygen areas at the bottom of the Bay.

Exploring the deep sea

Freediving: To 101m!!To 101m!!

Crawler gA gA Wally the Crawler 10 amazing deep sea creatures BBC: deep Blue: Amazing Creatures Benthic exploration

How do we test the water down below? The Godfather of deep water sampling:

What’s Down There? Reflection: Due day after presentations. One paragraph must analyze the strengths and weaknesses of your design. You should also reflect on how you managed the creative process. As second paragraph must analyze the design of your peers, and suggest the design of the perfect sampling device. To submit for common task uploading: This sheet with grade (scanned) Picture of your device or schematic (scanned) Reflection Task: You are the oceanographer and your task is to design and build a device that can retrieve a pure water sample from the depths. Being a highly qualified scientist, you know you cannot taint your sample with water from the water column. We want the benthic stuff. Tips: The water column from which you will sample is a 6 foot column of water, 12 inches in diameter. The column will be divided into a salt and fresh layer, each with their own color. Sample purity will be determined by a color comparison and salinity test using a refractometer. Tainting of the sample is also apparent by bubbling of the device on descent or ascent. When testing your device, avoid the bathtub. It is shallow and might lead you to believe your device will sink All devices must have a design that has the potential to obtain a water sample (a rock tied to a string will not get you a 70%)

Scoring Rubric Your device sinks, obtains a benthic sample, and returns to the surface with completely untainted water 95 Your device works nearly perfectly, but returns with a slightly tainted sample (as determined by salinity, color, or bubbling on descent or ascent) 85 Your device obtains a sample that has considerable tainting (as determined by salinity, color, or bubbling on descent or ascent), or it just does not work properly 75 Your device sinks, but has no ability to accomplish the task 70 Your device does not sink 60 **Up to 5 points for reflection +5