Marine Communities Exam 2

Terms: sexual selection, intra-sexual selection, intersexual selection, clones, gonochoristic, simultaneous hermaphrodites, sequential hermaphrodites, protandrous, protogynous, size advantage model, sexual dimorphism, polygyny, polyandry, sneakers, semelparity, iteroparity, anadromous, catadromous, oviparity, viviparity, lecithotrophy, planktotrophy, teleplanic, poecilogonic

Study Guide: Be familiar with examples of asexual reproduction.

• List and describe the pluses and minuses of sexual reproduction.  Be able to explain the Red Queen Hypothesis.

• List and describe the costs of free spawning. What mechanisms can prevent interspecific fertilization? Contrast broadcast spawning with internal fertilization.

• ? Define gonochorism. Differentiate between sequential (protandrous and protogynous) and simultaneous hermaphrodites.  Be able to give examples of each.  Under what environmental circumstances might you expect to find each of the three types of hermaphrodites? Explain the size advantage model and protandry. How do mating systems help to explain protogyny

• Using examples, differentiate between intrasexual and intersexual selection. 

• Explain the process that led to large claws of fiddler crabs and sexual dimorphism in elephant seals.

• Be able to tie parental care to sexual dimorphisms.

• Differentiate between semelparity and iteroparity and give examples.

• Differentiate between anadromous and catadromous fishes and give examples.

T/F: Sponges reproduce both sexually and asexually.

True, this is common.

• Asexual reproduction somewhat common in invertebrates, but vertebrates mostly sexual. Some parthenogenesis (unfertilized egg becomes fertilized spontaneously) in some vertebrates (like sharks).

• Mammals are all sexual as far as we know.

• It is weird that sexual reproduction is so common.

What are the costs to sexual reproduction?

Relative to asexual reproduction, sexual reproduction:

• Requires twice the fitness (both parents)

• Is less efficient

• Loss of “ideal” individuals? (because sexual reproduction takes two parents… the offspring will not be clones).

• Slower population growth rate

If there are so many possibly important negatives to it, why is sexual reproduction so common? Give ideas

The Red Queen Hypothesis:

• Differences in generation time between host and pathogen

• Pathogens adapt faster than hosts

• Increased host variation (sexual reproduction) makes it difficult for pathogen to specialize

• Genetic variation may slow pathogens down (this is why sexual reproduction is so popular, according to the Red Queen hypothesis)

Evidence: frequency of females (snails) gets smaller in areas with more parasites. Asexually reproducing. Snails are also smaller when parasites are more common.

KEY TAKEAWAY = Sexual reproduction is more common when there are more parasites. Fewer parasites? Asexual reproduction dominates.

Sexual reproduction is more common when there are ___ parasites?

more

_______ = Releasing eggs and sperm into the water, and sperm swim to the eggs. Planktonic larval stage.

Free spawning

Problems:

Fertilization success altered by currents – density matters. Currents can take them away.

Timing matters – males and females need to be in sync.

Sync with tides (like releasing at a full moon/spring tide).

Interspecific fertilization – gamete recognition proteins to help gametes find each other of their own species.

Polyspermy (multiply sperm to an egg)- there are blocks to prevent it.

Re – (this is a low Re world, very viscous) turbulence needed, as in the flagella on sperm.

_____ = You have males and females of a species.

Gonochorism

____ = Male and female parts at the same time.

Hermaphroditism

Ex: barnacles (simultaneous hermaphrodites)

What is the benefit of hermaphroditism?

Kinds:

• Simultaneous

• Sequential
  
  

  • Good for barnacles (simultaneous hermaphrodites) bc they can’t move and need to mate with whoever is around.
    
    

Protandrous [first male] (start as M, switch to F) — clown fish

Protogynous [first female] (F to M) – moon wrasses

What is the benefit of each?

Switching from female to male

protogynous - moon wrasses

Switching from male to female

protandrous - clown fish

At what size should a fish change sex?

Good explanation for protandry = this model says as you increase in size that could carry more eggs, advantage changes to become female.

There comes a size where fish would make more offspring as the other gender.

KEY: when smaller better to make babies by having sperm. When bigger makes more sense to be female and carry lots of eggs.

A form of sexual reproduction where two fusing gametes (sex cells) differ in size and/or form.

Eggs are bigger than sperm.

Anisogamy

Why protogyny?

• Related to mating systems

• When protogyny occurs, there is often a social structure where the largest male gets the harem.

  • Under protogyny, when large, can produce most offspring by being male

Why is polygamy more common?

• More common when resources are limiting.

• Why? Unequal competition

  • may not be 50/50 males & females

  • may have one male/female that is dominant competitor and gets lots of resources/habitat/food

____ = multiple females to one male

polygyny

Ex: pinnipeds like elephant seals

• some pinnipeds have extreme sexual dimorphism (the sexes look very different. In this case, males are a lot bigger)

____ = multiple males to one female

polyandry

Ex: seahorses

Albatrosses are _____, or have one mate.

monogomous

Polygamy makes sense when you have ____ resources

finite

Male seals often have a large harem of females. Females invest more in parental care. Which sex is the choosy sex?

Female fish has a group of male partners. Which sex is the choosy sex?

Female seals.

Male fish.

Pattern: whoever invests more in parental care is the choosier sex.

Polygamy – Which Sex is Choosy?

• Parental care investment important

  • Often, but not always female

• Females usually the choosy ones

  • Not always. Ex: Seahorses are the opposite.

• Choosy sex must determine most fit males to improve offspring life

Choosy sex leads to _____ _____.

Sexual Dimorphism

• Choosy sex estimating mate value by secondary characteristics

  • Leads to sexual dimorphism

• Intersexual selection

  • Females choosing the sexiest male

• Intrasexual selection

  • Males competing with each other

Females choosing the sexiest male

intersexual selection

Ex: colorfulness

Males competing with each other

intrasexual selection

• Theres a strong selective pressure for bigger body size for males

Ex: elephant seals fighting for access to the female harem

What organism is a simultaneous hermaphrodite?

barnacles, which is good because they don’t move

Investing in current offspring possibly at the expense of future offspring. Often females, but males also invest. The investing sex is often the choosy sex.

Parental care

Which narwhals mostly have the tusk?

Males, for sexual selection

Reproducing once. Ex: salmon, octopus

semelparous

Reproducing multiple times. Ex: humans, whales, etc.

iteroparous

Salmon are ______, because they migrate from sea to freshwater to spawn.

anadromous

Life History Strategies

Eels are _____. Opposite of anadromous. Spawn in ocean, spend most of their life in freshwater streams.

catadromous

Study guide lecture 9

Terms: uplankton, neuston, nekton, prokaryote, eukaryote, femto/pico/nano plankton, micro/meso/macro/mega plankton, diatoms, dinoflagellates, coccolithophores, cyanobacteria, red tides, Langmuir cells, holo/mero plankton, foraminifers, radiolarians, naupliar larvae, copepodite, krill, chaetognaths, cnidarians, appendicularians, ctenophores, patchiness.

wanderers; cannot swim against currents

plankton

seawater - air interface; mostly prokaryotes

neuston

swim against the current

nekton

______ are (mostly) photosynthetic prokaryotes and eukaryotes

• primary producers (gC/m3/time) (1o)

phytoplankton

____ are heterotrophic eukaryotes

• secondary producers (2o)

zooplankton

Prokaryotic heterotrophs

bacteria

u0.02 - 0.2 µm (viruses)

femtoplankton

picoplankton

u; 0.2 - 2 µm (bacteria)

u2-20 µm (small phytoplankton and bacteria) 

nanoplankton

If plankton < 20 µm, water must be observed directly

or filtered:  ____plankton  > 20 µm

Net

can be caught in plankton nets

u20 - 200 µm (small plants or animals)

microplankton

u0.2 - 20 mm (plants or animals)

mesoplankton

u2-20 cm (mostly animals)

macroplankton

u20-200 cm (mostly cnidarians)

megaplankton

T/F Plankton are good swimmers up and down.

true

How do you quantify phytoplankton?

uChl a (chlorophyll a) is measure of  biomass (g Chl a/m³)

uEasy to measure chemically

uSatellites sense color of surface water and use to map phytoplankton distribution

Phytoplankton are (mostly) photosynthetic prokaryotes and eukaryotes

• primary producers

What are kinds of phytoplankton?

diatoms

dinoflagellates

coccolithophores

cyanobacteria

uBrown/golden algae (Chrysophyta)

• Different from Phaeophyta

uA dominant net phytoplankton

• important to temperate spring blooms and in polar and neritic temperate waters

• not abundant in tropics

uAbout 100,000 species

uSilica for shell; transparent

Diatoms

uDominant net phytoplankton

• mostly in summer in temperate seas

• common in tropics 

uSize range: 25 µm - 1 mm

uRapid reproduction

u2 flagellae cause cell to whirl in water

uMostly unicellular with lower sinking rates

dinoflagellates

uNanoplankton; 5µm

uDominant in tropics or high-light conditions

uCalcium carbonate plates cover cell

uRemains common in many bottom sediments (cliffs of Dober)

coccolithophores

u prokaryotes

u nitrogen fixation common (nitrogen is most abundant gas in the atmosphere. In the ocean, the most limiting nutrient is nitrogen. Plants can’t use nitrogen gas. Nitrogen fixation is turning nitrogen gas into something that’s usable for them)

u Some produce toxins

u common in GOM (gulf)

cyanobacteria (blue-green algae)

HAB stands for?

Harmful algal blooms

• Some dinoflagellates (red tides), diatoms (Pseudo-nitzschia), cyanobacteria (Lyngbya) and other phytoplankton cause harmful blooms

• Toxins influence shellfish and marine animals

• Mass mortalities of fishes and benthos may result

• Some connection to fertilizer runoff??

What limits phytoplankton abundance?

Light

Nutrients

Grazing

Light limiting factor of phytoplankton abundance

• Light intensity linear on log scale only 5-10% reaches 20 m

• Light penetrates deeper in open ocean than in coastal waters (due to sediment suspended in the water that blocks light)

Nutrients limiting factor of phytoplankton abundance

Nitrogen:

• Nutrients – substance used by organism to grow, survive, reproduce

• N required for amino acids

• N2 gas abundant, but can’t be used by most primary producers

  • Must be converted to NH4+, NO2- or NO3-

• Soils on land are 0.5% N

• Seawater averages 0.00005% N

  • Surface water may have no free dissolved N (got taken up right away maybe)

• Nitrogen frequently limits phytoplankton in open oceans

• N2 fixed into NH4NO3 through industrial process for creating fertilizer

• Massive inputs of N from fertilizers reach coastal oceans today

Other nutrients:

• Phosphorus (PO4)

  • Animal excretion source of P

• Iron (Fe)

  • In open ocean (Pacific), Fe is very limiting

  • HNLP areas

  • The Geritol Hypothesis

• Silicon (Si02)

  • silicate limiting only in diatoms

Grazing limiting factor of phytoplankton abundance

• Many zooplankton and benthos consume phytoplankton at high rates

• Zooplankton somatic growth is slower than phyto and is more temperature dependent

  • zooplankton “lag” behind phytos in abundance

• Phytoplankton blooms may be necessary for successful recruitment of fish and invertebrates with planktonic stages

Reason you don’t have a lot more phytoplankton in more areas?

Not enough nitrogen

Why does diatom density drop in summer?

stratification, grazing, less nutrients

HNLP are areas in the ocean

High nitrogen low productivity

• not much phytoplankton, limiting nutrient is iron

uGiven what you know about sunlight, seasons, stratification, nutrients, and phytoplankton explain the diatom cycle depicted below (temperate bay).

1. Summer has increased sunlight, so why is there a decline in diatoms in middle of summer? During the summer, this water column is stratified, so most of the dissolved nutrients are trapped below the pycnocline.

2. Increase in zooplankton (grazing) that eat diatoms.

Goes back up in the fall since it is cooling, water column starts to mix, and diatoms pick up nutrients.

Diatoms bottom out in the winter because: lack of light

Why a huge bloom in the spring, bigger than summer? Getting more light again, water column NOT stratified yet so still lots of nutrients at the surface leftover from winter mixing.

KEY POINTS

• Lack of nutrients during seasonal stratification

• Lots of grazing

Remember nutrient & sunlight throughout seasons

____ are planktonic animals that are taxonimically diverse

u eukaryotes

u most protist and metazoan phyla

u Smallest are single-celled, nanoplankton-sized, protist heterotrophs (2-20 µm)

u Largest are jellyfish (> 200 cm)

zooplankton

_____ live their entire life cycle as plankton in water column. (5,000 species)

holoplankton (think holo = whole life are planktonic

_____ juveniles and adults are benthic but larvae are planktonic (500,000 species or more)

meroplankton

Many fishes and other nekton have ___ larvae

planktonic

• Many unicellullar phyla, includes foraminiferans (calcium carbonate shell), radiolarians (silica shell), microflagellates and ciliates

• Protozoans ingest bacteria, and remains create oozes in deep sea

• They are basis of paleo-oceanography

• data collected by coring the ocean floor

• Many eaten by small net zooplankton

protists

protists with calcium carbonate shell

foraminiferans

protists with silica shell

radiolarians

• Crustaceans

• Most important net zooplankton

  • “insects of the sea”

  • Important prey item

• Fecal pellets transfer nutrients to bottom

• 1 - several mm in length

  • weak swimmers that “jump” when attacked by predators

• Live in a high-Re but suspension feed in a low-Re environment on net-sized phytoplankton

copepods

Euphausiids are also known as ___. Important to polar food chains

krill

• Arrow worms

  • 1-3 cm in length

• predators of fish

  •   larvae and zooplankton

• 60 species

Chaetognaths

• Gelatinous, transparent or translucent

• reduced silhouette makes almost invisible

• Bodies a fragile sac that breaks up in nets

• Larger ones prey on copepods or small fishes; smaller species filter feed

Cnidarians, tunicates

Cnidarians include jellyfish, anemones, corals.

Tunicates include siphonophores. They are actually chordates, in the same phylum that humans are.

The largest migration on earth by biomass is by ___?

zooplankton (not all)

• Many zoops migrate daily – called ___ ___ ___

• Up to epipelagic at night and down to mesopelagic during day 

• May migrate 1000 m each way (typically 100-400 m below the thermocline)

• Equivalent to human walking 25 miles each night

• Highly variable.  Not all zoops do this.

• Can swim up 15 m/h; swim down 100 m/h. 

diel vertical migration

Why do zooplankton migrate? All these could be true.

1) Avoid visual-feeding predators at the surface
Supporting evidence

• Experimental support from lakes

• Reverse migration to nocturnal predators

Evidence against predation

• Zoops swim deeper than necessary to avoid predators

• Some transparent zoops also migrate

Reverse migration occurs in places where nocturnal predation (at night at the surface) is more important than predation by visual feeders.

2) Energy savings

• Cooler temps below the thermocline slow metabolic rate and conserve energy. They are poikilotherms (look up to confirm)

• Savings may be greater than the cost of extra swimming

3) Avoid harmful UV-light

• Carotenoid pigments protect some zooplankton but reddish/brown color increases visibility & susceptibility to predators.

4) Phytoplankton recovery

• Allows phytoplankton (the food source of zooplankton) to catch up during the day so zooplankton food resources aren’t exhausted.

• Zooplankton dive down during the day to give phytoplankton time to do photosynthesis and replicate.

• (will you find phytoplankton in mesopolagic? No, they need photosynthesis and mesopolagic doesn’t have much light)

T/F: Both phytos and zoops are patchy.

true

• Plankton from tandem tows differ greatly

• Satellites visualize patchiness of Chl a

Often offset;

• Chl a and copepods abundant in different “patches”

• due to grazing

Very little chlorophyll = very little phytoplankton (bc phytoplankton have chlorophyll in them)

Causes of patchiness include physical & biotic factors. What are they?

• Langmuir convection cells (move and concentrate/ aggravate plankton in certain parts and not others)

• Advection/turbulence may accumulate particles

• Localized zooplankton grazing may reduce phytoplankton

• Phytotoxins may eliminate zoops

• Consequence of patchiness

  • Patchiness causes large errors in estimates of population size

  • Increases work load and cost (more samples required)

Causes variation in one sample to the next

Not all phytoplankton are toxic

Something that is planktonic…

can’t swim against current

Lecture 10

Terms: mixing depth, critical depth, light compensation depth, photorespiration, photoinhibition.

„Explain the seasonal variation in phytoplankton abundance.  Draw figures and explain all of the processes that cause the changes in abundance.  How do plankton blooms differ between tropical and temperate waters? Describe the events occurring in a typical bloom.

„Explain the Sverdrup and Behrenfield models. How do they differ? How do they compare to the Seasonal Succession Model. Know these in great detail.

„Explain how LCD is affected by turbidity, proximity to coast.

„Draw and explain the nutrient cycles for N and P.  Include pools and sinks.

„Why are phytoplankton less abundant in the open ocean?

„Know the Redfield Ratio.  Be able to identify the limiting nutrient like we did in class.

„Explain benthic pelagic coupling.  What is it?  What mechanisms allow for the coupling?  What does it matter?

„Why is iron rare in the open ocean? Explain the whale pump and how it can affect phytoplankton abundance.

„Why is silicon important for phytoplankton?

„What evidence suggests that eutrophication (additional nutrients) favors HABs?  How might fertilizers favor dinoflagellates over diatoms?

„How do grazers affect phytoplankton distributions?

In temperate bays, diatom abundance is highest in the ___

Spring

Which figure most accurately depicts the seasonality of diatom blooms, surface nutrients, and zooplankton density in a temperate bay.

redraw and understand this

Differences in seasonal patterns do exist among taxonomic groups of phytoplankton

Diatoms passively sink

Dinoflagellates more mobile

Mostly focusing on diatoms

Build a study table of how these models differ in their explanations – remember that the pattern is the same, the explanation is what differs.

• the pattern is the same, its just different explanations for the pattern.

Diatom abundances decline in the winter due to_____?

What really goes on in winter & spring?

1% light reaches 100m in clearest of tropical waters, can be cm in turbid polar waters

Affected by season, latitude, and turbidity

Light compensation depth

• depth at which the amount of oxygen produced by   phytoplankton cell = oxygen consumed by respiration per cell

• Implications for phyto individuals and pop below this depth?

Critical Depth Hypothesis (similar idea to light compensation depth, but it is the whole population of diatoms rather than individual)

„Mixing depth – depth at which all water is thoroughly mixed due to wind or convection. Deeper in winter.

„Critical depth – the depth at which total O₂ production (photo) = total O₂  consumption (respiration). Net population growth is zero

„MD>CD = decreased phyto – too deep (winter) phytoplankton growth rates< loss rates. Diatoms are dragged to depths, not enough light. Tie back to class model of seasonal diatom blooms

„MD<CD = increased phyto (spring).  Shallower mixing depth, diatoms trapped by surface getting the light they need. Contributes to blooms.

„Summer growth still restricted by stratification and nutrients.  Fall mixing still explains fall bloom

„Sverdrup Model (1953) of Spring Phytoplankton Increase– works best with diatoms – more passive

Issues with Sverdrup model

„There are some blooms in the winter when there is little light, great MD, and low temps

„Blooms not always tied to MD

„Sverdrup doesn’t really look at r

Behrenfeld Model

„Focus on differences in winter and spring

„Also called Dilution Recoupling Hypothesis

„Pattern of seasonal mixing and stratification same

„Winter phyto density declines due to dilution from increased MD (not diatom abundance but density bc of greater mixing depth & they are dilutes/spread out over a greater body of water)

„Grazers (like zooplankton) also diluted from mixing = reduced grazing on phyto

„Abundance of phyto builds over winter (r is positive), although densities are low.

„Phyto population primed for spring sunlight

• bc everything is diluted, grazing pressure not as high. Zoop have hard time finding phyto bc everything so diluted. Contradictory to other models. He says diatom population is growing in the winter, so abundances of phytoplankton are going up.

  • how can population be growing but value be small? the y axis is density. even if growing its all spread out over a large volume of water so density will still be low.