Lecture 3- Primary production (Algae) Flashcards
What are the limiting nutrients in marine and freshwater systems?
Marine- nitrogen limited
Freshwater- Phosphorus limited
why do algae position at the thermocline during stratification?
To access up welling nutrients but also access sunlight
what are the four trophic stati of lakes? (in ascending order of Chla avaliability)
ultra-oligotrophic Oligotrophic Mesotrophic Eutrophic Hyper-eutrophic
which are the two un natural trophic lake stati?
Eutrophic and hyper-eutrophic
what are the three largest causes of phosphorous inputs into natural lake systems? (give percentages)
livestock (34%)
Sewage (34%)
Fertilizers (16%)
What are the consequences of eutrophication on biomass and species diversity?
Increased nutrient load causes sudden an increase in algae growth. This is turn causes an increase in overall biomass. However, cyanobacteria are often the dominating form of algae within eutrophication blooms, and these serve as a poor food source for other organisms within the water. This causes a reduction in predator populations (less food), and an overall reduction in species diversity as a result.
why do cyanobacteria reduce species diversity?
Cyanobacteria produce neuro toxins BMAA’s which cause neuro-degenerative diseases in life, and cause a decrease of species diversity
what is a gin-clear lake?
One dominated by aquatic plants
what is a pea-soup lake?
one dominated by cyanobacteria
how are pea soup lakes remidiated?
blasting them with hydrogen peroxide, essentially killing everything. this allows natural biota to re establish, and is the only effective remediation strategy
How do anaerobic conditions at the base of a lake impact phosphorous availability?
In aerobic conditions phosphorous is trapped within sediment at the base of lakes. However, when conditions become amaerobic, the oxidized microzone (which keeps phosphorus in solution) is dissolved, and phosphorous increases in solubility. It is then released into the water column, increasing overall concentration.
What is the oxidized microzone? how does it prevent phosphorus diffusion?
the Om is essentially a layer above sediments with e redox potential of 0.2 volts. it has a high ion absorption capacity, allowing phosphate ions to precipitate a ferric phosphate, preventing the diffusion of these ions into the water column.
what impact does anaerobic conditions have on the aquatic food web?
In extreme conditions, the invertebrates, vertebrates and primary producers can be lost, leaving only nutrients and the ANAEROBIC microbial loop
define a functional guild. give an example
a group of species that exploit the same environmental sorceresses in the same way, regardless of taxonomic position. Eg. Algae
what are algae composed of?
particulate organic carbon (POC)
