Chesapeake Bay 3.1 - Professor - Grace Brush PDF

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Professor - Grace Brush...

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Alizay Jalisi Johns Hopkins University ‘18 Principles of Estuarine Environment: Chesapeake Bay

3/1 Chesapeake Bay, Lecture 5: Chesapeake Organisms Pelagic - Open Water ● Plankton ○ Phyto ○ Zooplankton ○ Bacteria ○ Jellyfish ○ Fish ●

Swimmers (nekton) ○ Fish - anadromous

Benthic ● Producers ○ Algae ○ Submerged macrophytes (plants) ●

Herbivorous ○ Grazers

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Suspension feeders ○ Oysters

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Deposit feeders ○ Crabs

As salinity goes up (moving down the bay into more saline waters), pH goes down because clay becomes more positively charged Other important organisms Dinoflagellates - not preferred food by copepods (often found in marine phytoplankton) Cyanobacteria In upper surface of water Autotrophs, have a protective layer in the cell wall Eaten by protozoa and ciliates Blue-green algae Can ultimately block light from entering and contribute to eutrophication Submerged macrophytes Angiosperms - produce a flower that rests at the top of the water E.g. redhead grass, horned pondweed

Alizay Jalisi Johns Hopkins University ‘18 Principles of Estuarine Environment: Chesapeake Bay

Copepods Live for 80 days Has 12 stages of lifespan Eat diatoms Water flea Jellyfish Feed on larvae of oysters Oyster Sexual stage in the summer: release eggs and sperm into water, but unfortunately very few eggs are actually fertilized -- less than 1 in 10,000 survive the larval stage Poached/ harvested via aquaculture, hunted by colonizers, and conservation efforts have been not always successful Crabs 10 legs - crustacean while front legs are used for swimming Larvae are planktonic, released by females in high salinity waters See image on life cycle of blue crab Discussion of Papers 1. Boynten et al 2. Conley (ME) a. Summary ● This paper explores how changes in DSi (dissolved silica) caused by humans dumping N and P into the freshwaters affect other biogeochemical cycles, species composition, food web dynamics, nutrient cycling in the Great Lakes ● We often talk about the impact of N and P on eutrophication but don’t get enough into changes in silica levels which diatoms (diatoms are food for copepods) depend on ○ Last lecture, we talked about how diatoms (types of algae whose cell walls are composed of hydrated silica) ● Cultural eutrophication -- human activities and pollution speeding up a natural process ○ Declining oxygen levels, fish ● Hypothesis: limitation of diatom flora due to reduced DSi → undesirable changes in marine ecosystem such as changing phytoplankton flora ● Long term changes in … ○ Nutrient loading (how much P is in the lakes?): fig 2 ○ [Dsi] fig 3 ■ why are there seasonal differences?

Alizay Jalisi Johns Hopkins University ‘18 Principles of Estuarine Environment: Chesapeake Bay

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Nutrient enrichment ■ P enrichment → diatom population goes up → [DSi] goes down ■ Investigated globally in lakes, rivers and coastal areas ■ Revisiting what we discussed about the bay last week ● Pp. 9 or 187 ■ Non-diatom phytoplankton can go up ○ Paleolimnological studies ■ 2 stages of DSi depletion: ● 1. In the summer, depletion from surface waters ● 2. In the winter, reserves from the rest of the water column are depleted, limiting diatom pop for the rest of the year ■ Gets worse with each year, limiting recovery b. Interesting/ Confusing Points/ Discussion Questions ■ We need to reduce point loads because we cannot otherwise affect the DSi content in the waters as Boynton paper mentions 1. What are some ways that we can do this? How can we advocate for this in our local communities? ■ What food webs are affected?...