Simulation labs for Biology 4263

• I will discuss Limiting Nutrients and Competition, Go Fish, and Oil spills.

• Background material covered :– Limiting Nutrients and Competition – Go Fish – Oil spills

Limiting Nutrients and Competition • Algal growth is dependent on the availability of

sunlight and essential nutrients including nitrogen, phosphorous, and iron

• This lab considers the availability of sunlight to the growth rate of hypothetical green algae and the three nutrients to green, blue, and red algae by themselves and in combinations

• The objective of the laboratory exercise is to explore how nutrient availability can influence competition between species of algae

Background Information

Are phytoplankton adapted to light intensity?

• Pmax is the intensity of light at which photosynthesis is maximal– optimum light intensity

• Pmax - light intensity relationship for different types of phytoplankton suggests adaptation– diatoms versus dinoflagellates

Diatoms reach Pmax at low light levels

Dinoflagellate photosynthesis maximal under high light intensities

Nutrients:

• Various nutrients can be limiting and the kinetics of nutrient uptake is important

• Limiting nutrients include N, P, Fe, Si• Nutrients enter phytoplankton cells by

active transport– surface area/volume is important to phyto

body size

Nitrogen • Required for amino acids• Soils on land are 0.5% N• Seawater averages 0.00005% N– Surface water may have no dissolved N

• Nitrogen frequently limits phytoplankton in coastal oceans

More on nitrogen

• Massive amounts of N from fertilizers reach coastal oceans today and is the most important cause of eutrophication

• Ammonium (NH4), nitrate (NO3) and nitrite (NO2) are possible forms

More on nitrogen

• Most phytos prefer ammonium but can use nitrate

• N fixation (from N2) important in some locations like estuaries

• Inputs from many sources and nitrogen cycle is complex with many bacterial transformations

Other nutrients:• Phosphorus (PO4)– Animal excretion is a source of P

• Iron (Fe)– In vast areas of the open ocean (Pacific), Fe is

limiting– Why iron?– The Geritol Hypothesis

• Silicon (Si02)– silicate limiting only in diatoms

Nutrient kinetics Rate of uptake depends on nutrient

concentration (to a point)• V (uptake rate) = Vmax * S / (ks + S) where S =

concentration of a limiting nutrient, Vmax = maximum uptake rate and ks = half saturation constant (the nutrient concentration at Vmax/2)

Vmax

Go Fish: Fisheries Management Techniques• Collapse of fisheries stocks :

• NMFS – 45% of the fish stocks whose status is known are being overfished• Why do fisheries collapse ?

– Overfishing– Environmental factors – climate change, change in salinity, pollution– Ecological factors – changes in predators or prey – fishing down the food web (Essay to accompany this report)• Pauly • Worms et al. • de Musert et al. 2008

• Sustainable strategies – Maximal sustainable yield (MSY) – popular but often unsuccessful– Constant effort– Adaptive methods

• Squonkfishery

Oil Spills : Population Growth• Oil eating bacteria –PWS, Dr. Ralph Portier• Logistic equation – simulations of population

growth– Bacterial division rates– Oil (food) availability

Incomplete Applications• Must be completed by tomorrow at 4:30 PM or

can’t be registered• Two people – notarized participant agreement– Millie Dave– Sumit Patel