Title: Biogenic Sediment Distributions Category: Chemical Subcategory: Difficulty: Unknown Year 2004 Bowl: Shore Bowl Author: C. Grant Law Contact info: ext 310 IMCS, Rutgers University 71 Dudley Rd. New Brunswick, NJ 08901

QUESTION Round:Time: 4 minutes Difficulty: ModerateStandard/Category: Chemical QUESTION: The following figure shows the distribution of common sediments on the seafloor. 1)Calcareous and siliceous sediments are biogenic. Name 2 organisms that are primarily responsible for these two sediment types? (2 points each) 2)Why are siliceous oozes found where they are? (4 points) 3)Why aren’t siliceous oozes found elsewhere? (4 points) 4)Why are calcareous oozes found where they are? (4 points) 5)Why aren’t they found elsewhere? (4 points)

ANSWER Round:Time: 4 minutes Difficulty: Moderate Standard/Category: Chemical QUESTION/ANSWERS: 1) Calcareous and siliceous sediments are biogenic. Name 2 organisms that are primarily responsible for these two sediment types? (2 points each) ANSWER: Siliceous sediments are primarily created by diatoms or radiolaria (2 points). Calcareous sediments are primarily created by coccolithophores and foraminiferans (2 points). 2) Why are siliceous oozes found where they are? (4 points) ANSWER: They are regions where large scale diatom blooms are common. 3) Why aren’t siliceous oozes found elsewhere? (4 points) ANSWER: The entire ocean is under-saturated in silica, so siliceous sediments dissolve. Where the input of siliceous sediment is less than the loss due to dissolution, siliceous sediments will not be found. 4) Why are calcareous oozes found where they are? (4 points) ANSWER: Below a certain depth, the pressure, temperature and pH of seawater cause calcium carbonate to dissolve. For this reason, calcareous sediments are only found in regions where the seafloor lies above that critical depth. 5)Why aren’t they found elsewhere? (4 points) ANSWER: Calcareous sediments are absent from regions where the seafloor lies below the critical depth, where they are dissolved and where they are diluted by input of other sediments. Sumich, JL, An Introduction to the Biology of Marine Life. Wm. C. Brown Publishers. (Fig. 11.1)