Exam 2 Flashcards
What is the largest source of biologically-active Nitrogen?
The atmosphere (6.2%)
Where is most of Earth’s Nitrogen located?
The Lithosphere (crust)
Which forms of nitrogen are the most biologically important?
Ammonium (NH4+)
and
Nitrate (NO3-)
Transformations of Nitrogen
Fixation
Uptake
Mineralization
Nitrification
Denitrification
N Fixation
What is it? Who does it?
N2 -> NH4+
Cyanobacteria
Rhizobia
Fertilizer Production - Haber Bosch process
Uptake
NH4+ or NO3- taken up by organisms and incorporated into ORGANIC NITROGEN (Amino Acids)
Mineralization
Organic N -> NH4+
Nitrification
NH4+ -> NO2- -> NO3-
Occurs when oxygen is present
Low light
Denitrification
NO3- -> N2O -> N2 (atm)
Occurs in anoxic conditions, bacterial process
AKA Nitrate Respiration
N Cycle (Basic)
Epilimnion N Cycle
Hypolimnion N Cycle
What forms of Nitrogen are present when O2 is present?
ALL OF THEM
N2, NO3, NO2, NH4, Organic N
What forms of Nitrogen are present when there is NO O2?
NO3 disappears –>–> N2(g)
NH4+ Accumulates
What does the N Profile of an Oligotrophic lake look like during stratification?
What does the N Profile of a Eutrophic Lake look like during stratification?
What is the Redfield Ratio?
106 C : 16 N : 1 P
The ratio applies to plankton and algae in aquatic systems
Which nutrient limits biological activity in inland waters?
Phosphorus
(Nitrogen in the Ocean)
Where do most primary producers occur in a water column?
Epilimnion/Photic Zone
Picoplankton
0.2 - 2 µm
High SA:V ratio allows rapid growth
Small size makes susceptible to grazing
Nanoplankton
2 - 30 µm
Still small
susceptible to grazing
Microplankton
30-200 µm
Larger
Sink faster
grow slower
less susceptible to grazing
dominant in nutrient-rich lakes
Algal Divisions
Cyanobacteria - blue/green algae and bact
Chlorophyta - green algae
Bacillariophyta - diatoms
Pyrophyta - dinoflagellates
Cyanobacteria
PROKARYOTES
Often dominant
All types of environments
Some fix Nitrogen
Some produce toxins
Buoyant (gas vacuoles)
Chlorophyta
Green algae (standard algae)
EUKARYOTES
common in eutrophic and hypertrophic lakes, many streams
Bacillariophyta
Diatoms
Require Silica to build their FRUSTULES
Biodiverse
Heavy –> limited mobility
Pyrophyta
Dinoflagellates
Brownish color
often “armored”
cause RED TIDES in marine systems
Seasonal succession of phytoplankton
- Initial bloom after mixing
- Grazers increase, phyto crash (“spring clear water phase”)
- Grazing declines, summer bloom (greens and blue-greens)
- Fall cooling and grazing
- Fall blooms post-mixing
What are the two main groups of primary producers?
Algae
Macrophytes
Periphyton
Algae growing on benthic sediments
Epiphyton
Algae growing on plants
What are the 3 Macrophyte growth forms?
Emergent
Floating Leaved
Submergent
Macrophyte Physical Adaptations
NO structural tissue
NO waxy cuticle
Aerenchyma (buoyant tissues)
Heterophylly (“diverse leaves”)
Contributions of different Primary producers to overall lake productivity
HNAN
Heterotrophic Nanoflagellates (Type of PROTOZOAN)
Non-pigmented species made of:
- cryptomonads
- dinoflagellates
- euglenoids
- chrysophytes
Ciliates
Type of PROTOZOAN
Heterotrophic zooplankton that can live in hypoxic conditions
some are predators
some have multiple modes of nutrition
Rotifers (Phylum Rotifera)
A relatively large phylum of zooplankton that are multicellular, mostly non predatory, and grow quickly
PARTHENOGENIC REPRODUCTION
Parthenogenic Reproduction
Under favorable conditions, female rotifers and bythotrephes will undergo amictic reproduction, in which they produce a viable egg that matures into an amictic female
Under UNFAVORABLE conditions, a female lays an egg that needs to unite with sperm from a HAPLOID male to form a fertilized resting egg.
Types of Crustaceans
Cladocerans (Daphnia)
Leptodora (Predatory-raptorial)
Bythotrephes (Spiny Water Flea)
Copepods (Calanoids and Cyclopoids)
Chaoborus
Insect larvae from insect order Diptera
Anti-Predator strategies of Zooplankton
Vertical Migration
Cyclomorphosis (Morphology changes with seasons and generations - spinier with predators around)
Zoobenthos Taxonomy
Porifera - Sponges
Cnideria - Hydras, jellyfish
Bryozoa - Phylactolaemata (related to corals)
Annelida - Aquatic Worms
Crustacea - Crayfish
Mollusca - Snails and bivalves
Aquatic Insects
Size distinctions of zoobenthos
Macrobenthos (>500 um)
Meiobenthos (100-500 um)
Microbenthos (<100 um)
Feeding Groups of Zooplankton
Filter-feeders
Deposit-feeders/collectors
Scrapers/grazers
Shredders (leaves)
Predators
Zoobenthos ________ in fish diets with increasing lake size
DECREASES
Fish Taxonomic Groups
Jawless - Lampreys
Cartilaginous - Sharks & Rays
Bony - Lung fish, ray-finned fishes
Major Freshwater Fish Orders
Cypriniformes - Minnows
Siluriformes - Cat Fish
Perciformes - Perch, walleye, darters
What are the most imperiled organisms on the planet?
Freshwater fishes and invertebrates
Especially large fishes
Fish Feeding Groups
Piscivores - Eat fish
Benthivores - Bottom-feeders (tentacles)
Surface Feeders - falling insects
Zooplanktivores - small mouth on body
Omnivore - generalized
Reproductive strategies of fishes
(All Egg layers-varying amounts)
Mouth-brooders
nest builders
lay-and-leave
What are some roles that fishes play in ecosystems?
Littoral-pelagic
Bioturbation - carp stir sediments
Upstream migration (salmon)
Control of Zooplankton Community
Overview of Lake Biota (Major Groups Present)
Phytoplankton
Zooplankton
Fishes
Benthic Plants
Zoobenthos
Bacteria
Eutrophic
Well Fed
Green, shallow, human activity in watershed
High phytoplankton production
Oligotrophic
Poorly-fed
Deep water, clear/blue
Low production
Mesotrophic
Transitioning from oligotrophic to eutrophic
Dystrophic
Brown, lots of DOM
Wetlands in Watershed
Light limited
What variables are used in the Carlson State Index?
TP
Chlorophyll-a
Secchi Depth
What are some management practices that treat the SYMPTOMS of eutrophication?
Increase algal grazing (manip. food web)
Kill algae (CuSO4)
Reduce Light Avail (Aquashade)
What are some BMP’s for treating the CAUSES of eutrophication?
Decrease impervious surfaces
Plant Trees (nutr uptake)
Build more retention ponds (nutrs absorbed before water flows to lake)
