Basisc of aquatic bioloogy

Question 1

Ecology

Answer 1

Scientific study of the interactions that determine the dirstributions and abundance of organisms.

Distribution and occurance that we see today are the product of previous.

Question 2

Fitness

Answer 2

Measure of a genoytpes’s long term success

• Individuals that produce the largest number of offspring over a long period of time have the greatest fitness.
• Fitness is always a relative measure.
• Two components: reproductive potential and survival

Maximum possible fitness never achieved nature Optimization instead.

Question 3

Abiotic factors

Answer 3

• Temperature
• Oxygen
• pH
• Ions
• Water flow in streams
• Density and surface tension

Question 4

Temperature

Answer 4

• narrow range of T fluctuations
• Lethal limits of T are less important
• False T dependencies (e. g. warm water contains less O2)
• T very important for regulation of speed of biochemical and physiological processes

Question 5

Qxygen

Answer 5

• Very important!
• O2 input only at surface
• Productivity and morphometry determine O2 balance and vertical distribution
• Organic poluution can lead to O2 reduction or depletion
• Vertical uneven distribution of O2 in lakes O2 deficiencies and anoxie conditions also in
  streams
• Groundwater and springwater are often low in O2

Question 6

Adaptaions to limited or changing O2 concentrations

Answer 6

Adaptations have their limits. O2 deficiencies are very critical for aquatic organisms

• Whole body surface as surface area for gas exchange
• Life in water, but use atmospheric O2
• Supply air bubble attached to body
• Haemoglobin with high O2 affinity
• Diapause
• Anoxibiosis

Question 7

pH

Answer 7

pH is in turn affected by biological processes

• Direct Effects:
  Physiological damage or dysfunction
• Indirect effect on water chemistry
  o Dissociation of ammonium
  o Calcium-carbonic acid equilibrium
  o Solubility of metals

Question 8

Other ions

Answer 8

• Hypertonic regulation is essential to avoid invasion of excess water and loss of ions
• Great energetic cost, because body membranes cannot impermeable, so active uptake and removal against the gradient
• Few species can live at boundary between salt and fresh water
• Calcium is usually the dominant cation and carbonate or bicarbonate the dominant anion in freshwater. Ecologists often relate occurrence of species to calcium concentration
• Freshwater individuals: Have to maintain ion (constantly pump) → Loss of energy
• Brackish water: Very specialised

Question 9

Water flow in stream

Answer 9

Morphiologcal and behaviourla adapations to cope with all these challenges.

• No vertical gradients, except for light
• Water shear force
• Import and export (Never constant) → Filtering organisms
• Selective transport of sediments, thus different type of bottom depending on stream velocity
• Unidirectional drift, both dangerous and useful

Question 10

Resources

Answer 10

• Light
• Mineral Nutrients
• Dissolved inorganic carbon
• Inorganic sources of energy
• Anerobic respiration
• Dissolved organic substances
• particulate organic substances

Question 11

Light

Answer 11

Light is not a boundary condiytion for photosynthesis. It is a consumerable resource

Question 12

DIC

Answer 12

Dissolved inorganic carbon

• DIC major forms:
  o CO2 (aq) (aqueous carbon dioxide – dissolved gas)
  o H2CO3 (carbonic acid – trace amount)
  o HCO3 - (bicarbonate ion)
  o CO3 -2 (carbonate ion)

Plants need CO2 (aq)

Alternative strategies when CO2 in water becomes limiting:
* Aerial leaves in macrphytos
* Use of CO2 in pore water of sediments
* Temporal decoupling of photosynthetic light reaction
* Utilizations of bicarbonate

Question 13

Mineral nutrients

Answer 13

• Theoretically all elements could be limiting factors, but typically in freshwaters only N, P and some trace elements can become limiting.
• Redfield molar stoichiometric ratio 106C : 16N : 1P
• Approximation, very variable in inland waters
• Only dissolved forms can be uptaken by organisms

Question 14

Inorganic sources of energy

Answer 14

Chemolithoautotrophic bacteria are extremely important for nutrient cycling in freshwater.

Question 15

Anearobic respiration

Answer 15

• Heterotrophic bacteria use DOC as source of carbon and energy, but cannot use oxygen as a terminal electron acceptor in respiration
• Instead, oxygen-rich compounds are used to oxidize organic matter:
  o nitrate NO3- → denitrification
  o sulfate SO42- → desulfurication

Question 16

DOC

Answer 16

Dissolved organic carbon

• Most of organic matter in lakes is dissolved (ratio dissolved : particulate = 6:1 or higher)
• Sources
  o excretion of living organisms
  o cell breakdown (autolysis)
  o microbial decomposition of dead organisms
  o allochtonous sources (e.g. soil runoff, discharges)
• DOC is a mixture of several substances
• Mostly important as source of energy and carbon for bacteria, but also used by protists and some algae.
• Very rarely by eucaryotes.

Question 17

POM/POC

Answer 17

Particulate organic matter/carbon

• POM or POC occurs as either living or dead matter (detritus)
• Detritus can either be formed within the water system (autochthonous) or be imported from outside (allochthonous, e.g. leaf litter)
• In streams POC can be exclusively detritus. In lakes proportion of living matter is usually larger, due to large amounts of algae
• Examples of important particulate-feeders: shredders (reduce particles’ size), scrapers (“graze” on algae and on microorganisms), sediment feeders (ingest sediment and assimilate organic matter), filter-feeders (particles are ingested through water current)

Question 18

Population

Answer 18

Defintion of population depends an the abjective and on the scale of the observer

Natural selections works on individuals, but to occur it needs a group of individuals of the same species with different characteristics that occupy a particular location at a given timer (population)
Population as “reproductive system or gene pool”
* Rerely completely closed (gene flow)
* Phenotypic or genotypic variation
* They can have age structure
* Specific spatial distribution pattern
* Size and density can vary
* Space depends on size and mobility of individuals

Question 19

Population size

Answer 19

• Abundance is the density of organisms in s defined surface area of volume of water
• Relative abundance
• Abundance of populations changes temporally and spatially (fluctuations, cyclic oscillations, long-term trends)
• Major differences among species
  o e.g. phytoplankton density in temperate zones can have seasonal fluctuations over 4 orders of magnitude
  o longer-lived species (higher plants, fish, mussels) fluctuate much less, mainly due to several year classes
• Abundance changes through reproduction, mortality, import and export

Question 20

Demography

Answer 20

Skizze

Type III most common in freshwater:
* Animals do not care for juveniles, but produce large numbers of offspring
* High mortality rate among juveniles
* High probability of surviving after critical age is reached
* Random mortality amongst remaining age groups
* Rarely in nature is any one of these patterns strictly followed. Usually organisms present some combination of the three curves
* Not all individuals contribute equally to the maintenance of the population (juveniles do not produce offspring and later n° of offspring is age-dependant)
In natural conditions, populations tend to reach stable age distributions. Upon new colonization or environmental disturbance, achieving this equilibrium can take several generations.

Question 21

Distribution

Answer 21

Random
* Species that do not control their movement

Even
* More typical for species with negative influence among individuals
* Common in streams, not lakes

Clumped
* Microhabitats in streams
* Vertically in the homogenous pelagic regions of lakes
* Clouds or swarms, offer security from predators.

Question 22

Communities or Bioconenoses

Answer 22

A system of populations that are bound to one another by strong interactions and surrounded be a surface of weaker interactions with populations outside the community

• Often defined a priory, without measuring strength of interactions
• Often defined by common functional characterisiscs rather than by assumed strong interactions

Question 23

Interactions

Answer 23

Reason is generally to be found in interactions between populations. → Most species have a more limited distribution that it would be predicted by their physiological tolerance.
* Competition for resources, for space or for position
* Allelopathy or Antibiosis: Direct effect of competitors through release of chemicals that inhibit other species

Question 24

Predator -Prey relationship

Answer 24

All interactions that result in energy transfer from one organism to another, and represent a mortality factor tor the prey.

Being eaten is the most important biotic cause of morality

Question 25

Evolution of defence mechanisms

Answer 25

Many features of the morphology, life history and behaviour of aquatic can be explained through this co-evolution (“arms race”)

Question 26

Grazing on Phytoplankton

Answer 26

Predator-prey interaction where algae and bacteria are the prey organisms and herbivorous zooplankton is the predator.
Grazing explains the clear-water phase in lakes in the middle of the growth period → transparency similar to middle of winter. Regeneration of dissolved nutrients through zooplankton grazing.

Question 27

Feeding seslctivity of the herbivorous zooplankton

Answer 27

Grazing of zooplankton is selective, since many algae and cyanobacteria have ingestion-resistance characteristics/mechanisms
* Size and bulkiness
* Toxins
* Chemical qualities “taste”
Alternatively digestion-resistance protections (e. g. thick cell walls or stable mucilaginous sheath), so that they are ingested and egested still alive (even take up nutrients from predator’s guts)

Question 28

Grazing on periphyton

Answer 28

Periphyton includes not only algae and cyanobacteria growing attached to submerged surfaces, but also heterotrophs (e. g. herbivorous protozoa)
Grazer (benthic microfauna) exert pressure on microalgae, but at the same time release them from “internal” grazing pressure.
Grazing selectivity shows far more complicated patterns than for plankton. E. g. greater differences in size and taxonomic origin of the grazers, different abilities to adhere to substrate, etc.

Question 29

Vertebrate Predators

Answer 29

Planktivorous, benthic and piscivorous fish and amphibians

• Most fish orient visually, catching individual prey, but there are also filtering fish (they pump water and retain plankton)
• Reaction distance is shorter in turbid or highly colored water or at low light intensity
• Some fish species switch to feed on benthos as they get older
• Optimal prey-size and trade-off with energy required to ingest prey
• Trade-offs between prey availability and exposure to predators

Question 30

Invertebrate predators

Answer 30

Several invertebrate species are omnivores and predators. Contrary to vertebrates, they do not have highly developed eyes and detect their prey be mechano- or chemoreception.

Question 31

Defences og the prey

Answer 31

• Reducing detectability through transparency or colour adaptation
• Escaping by fleeing or by preventing successful handling by the predator
• Reducing detectability decreasing turbulence
• Diel cycles (e. g. hiding during the day)
• Chemical defences (e. g. poision glades or being distasteful)

Question 32

Parasitism

Answer 32

• Predator-prey relationship in which the “predator” (parasite) is considerably smaller than its prey (“host”) and lives in close association with it
• Endoparasites live within the host
• Ectoparasites live on the outside of the host
• Many parasites of land animals have a stage that passes through water
• Parasitism does not always harm the host (“gentle parasites”), but always cause a reduction in the growth of the body or population

Question 33

Symbiosis or mutualism

Answer 33

• Interactions are positive for both parties
• Generally more important in land communities, but also numerous casas in freshwater

Question 34

Internals structure of communities

Answer 34

Food chains
* Traditional Concept
* Linear transfer of energy and matter between trophic levels
* Too simple for natural systems (except for extremely species-poor habitats)
o Filter-feeding organisms select their food based an size and not on trophic role
o Planktivorous fish eat both “herbivorous” fand “carnivorous” zooplankton
* Not so easy to assign organisms to specific trophic levels
* 90 Percant engeriy loss

Question 35

Food webs

Answer 35

Guild is a functional category used in food webs: group of species that exploit the same resources or different resources in related ways.