lecture 6: single cell plankton (marine communities)

lab report for the field course

• will be put in canvas

plankton diversity

Plankton communities are taxonomically and functionally diverse

• definition of plankton →

  • they drift

  • cannot actively swim against currents

• organisms that can be pluricellular to unicellular

• plankton diverity can be found across several lineages form viruses to bacteria/archaea and eukaryotes, both unicellular (protists/micro-eukaryotes) and multicellular

• size range:

  • picoplankton

  • nanoplankton

  • microplankton

  • mesoplankton

  • macroplankton

  • megaplankton

• today only unicellular eukaryotes

size-based framework

plankton size classes

• Plankton classification was ecologically inadequate

• The traditional division of plankton is overly simplistic and taxonomically inconsistent:

  • bacterioplankton

  • phytoplankton

  • zooplankton

• It blurs important ecological distinctions like mode of nutrition, reproductive rate, and trophic role

• so instead of the above classification, it was changed to different terminology:

  • viroplankton

  • bacterioplankton

  • mycoplankton

  • hytoplankton

  • protozooplankton

  • metazooplankton

  • nekton

• then there is the other temrinlogoy for plankton (look at the diagram in teh slide)

  • femtoplankton

  • picoplankton (<2 (3) µm)

  • nanoplankton (…)

  • microplankton

  • mesoplankton

  • macroplankton

  • megaplankton

• This is because it makes it easy to classify them according to the amount of energy they consume

• emphasis on size-based calssification

• advocates for organising plankton by size fractions (femto-, pico, nano, micro, meso, macro, mega) to align with:

  • sampling methods

  • metabolic scaling

  • trophic interactions

plankton size range and available optical imaging methods

• flow cytometry mostly used for pico and nano plankton (0.2-20µm)

  • insitu imaging equipment

• flow cam

  • different types of flow cams

  • insitu imaging equipment

  • 50 - 200 µm

• zoo scan

  • 200 - 2000 µm

plankton size range and sampling methods

• The difference between using a wp2 net and a phytoplankton net is becasue the amount of water samples is more using a wp2 net than with a phytoplankton net

functional diversity

plankton communities are functionally diverse

• phytoplankton →

  • photosynthetic prokaryotes (cyanobacteria)

  • microbial eukaryotes

  • several lineages

• zooplankton →

  • heterotrophic uni and multicellular eukaryotes

  • protozooplankton and metazooplankton

• mixoplankton →

  • microbial eukaryotes exhibiting a combination of autotrophy and heterotrophy

planktonic protist functional groups based on mechanisms for energy and nutrient acquisition

• phago-heterotroph

• photo-autotroph

• constitutive mixotroph

  • behaves like a consumer

• generalist non constitutive mixotroph

  • eats anything

  • but when it eats an algae, it keeps teh chloroplast temporarily and photosynthesizes for that time period

• endosymbiotic specialist non-constitutive mixotroph

• plastidic specialist non constitutive mixotroph

marine planktonic protists

protists = single celled eukaryotes

• protists are more abundant than all animals together

• planktonic protists are hte engine of marine ecosystems

eukaryotes have invested in cell forms, apparatus and lifestyle

• plasmodium and toxoplasma have evolved from free living algae

  • apicomplexans harbour a unique organelle called Apicoplast which is a non-photosynthetic chloroplast

• ciliates and the algae symbiodinium are genetically closely related

  • they belong to the alveolata, a very diverse group of protists

  • they are from a diverse group that evolved from algae

eukaryote phylogeny before the molecular era - a brief history

• ernst haeckel: the plankton artist

haeckel - general morphology of the organism

• enrst haechel believed that the natural system proposed darwim (1895), should be represented as a geanological tree

• haeckel’s book provided major imporvements to teh theory of descent, including:

  • a large vocabulary of neologisms, some of which became succesful, such as phylogeny, monophyletic, and polyphyletic

  • the term protists (the first of all or primordial) to distinguish unicellular organisms

haeckel - pedigree of man

• metazoa - today use to describe multicellular animals

• the use of phylogeny to establish series of ancestral morphological characters

eukaryote phylogeny in the molecular era - 2000s

• most of the supergroups had at least one morphological synapomorphy (a characteristic present in an ancestral species and shared exclusively by its evolutionary descendants)

• the precise number and membership of the supergroups has varied, reflecting the rapid pace with which importnat taxa are being discovered and added to the tree (broad molecular phylogenetic analyses)

orphan taxa - Metamonada and Discoba

Discoba - Euglenoids

• discoba consists of four main lineages: Jakobida, Euglenozoa, Heterolobosea, and Tsukubamonadida

  • Euglenozoa are a group of >1500 described species of single-celled flagellates with diverse modes of nutrition, including phagotrophy and photoautotrophy

  • upiquitous flagellates

  • covered with rigid pellicle allowing euglenoid specific motion (metaboly)

  • notes from video about euglenoids:

    • mostly found in freshwater

    • get food through phagocytosis

    • they dont have chloroplasts, instead they rely of feeding mechanisms like phagocytosis and osmosis

    • however, the older ones of these ingested green algae, and took the algae’s chloroplast and the rest of the photosynthetic apparatus, evolving the ability to make their own food in addition to consuming nutrients from their environment

    • the common link between the euglenoids is the striped surface called the pellicle, other than that, there is nothing else.

    • the most common shape among euglenoids is a sort of elongated almond shape and the end comes to a tapered point

    • then there is th emonomorphina pyrum, whose bodies are round and have a clear tail coming out from one end

    • almost all the Phacus species have a flat diamond body, resembling a leaf, and some Phacus helicoides can twist the leaf into a corkscrew structure; they have a pellicle, but are rigid and can’t engage in metaboly (euglenoid movement)

    • all photosynthetic euglenoids have two or more flagella, even if they are capable of metaboly

    • the eyespot in eugelnoids works as a shading device, telling the cell where it can find light to drive photosynthesis

    • the chloroplasts in the euglenoids are different from their ancestral counterparts, particulary in how they store their energy

      • green algae create a starch that is stored in the chloroplast that is used later for their energetic needs, but Euglenoids produce a different carbohydrate called paramylon that is kept in the cytoplasm of the cell instead of the chloroplast

  • Symbiontids are anaerobic deep-sea microbial eukaryotes with sulfur or sulfide oxidizing epsilon proteobacteria epibionts

  • kinetoplastids are ubiquitous flagellates, free-living (bodonids) or parasitic (trypanosomes)

Supergroup Amorphea - Opisthokonts

• amorphea is robustly supported in most phylogenomic analyses

• there is a great diversity of lifestyles and morphologies among unicellular opisthokonts

• there is a larger diversity of basal lineages on the animals side of opisthokonta, including the Icthyosporea

• sister-group to Metazoa = Choanoflagellata

supergroup Archaeplastida - Glaucophytes, Phodophyta and Chlorophyta

Primary endosymbiosis

• the first one occurred ~1.6 billion years ago and gave rise to glaucophytes, red algae and green algae (the ancestors of all plants)

• the second one occurred ~90-140 million years ago, establishing a permanent photosynthetic compartment (the chromatophore) in amoebae in the genus Paulinella

Chloroplastida

• Chloroplastida or Viridiplantae includes two evolutionary branches:

  • Chlorophyta (dominated Proterozoic oceans): form a large and morphologically diverse clade of marine, freshwater and terrestrial green algae

  • Stretophyta: include a paraphyletic assmeblage of green algae (charophytes) and the land plants

• it is one of the main groups of photosynthetic eukaryotes

supergroup Cryptista - Cryptophytes

• Cryptophytes, a lineage that has been central to the stufy of secondary origin of chloroplast

• chryptophytes plastids (red algal origin) is surrounded by four membranes; presence of a nucleomorph (NM) = residual nucleus of the red algal endosymbiont

• they are ubiquitous in marine, brackish, and freshwater habitats

• mostly photosynthetic with some mixotrophic species

• because they produce PUFA, it’s used as food for copeopds in fish farming

• chlorplast contains phycobiliprotein (phycoerythrin)

supergroup Haptista - Centrohelida, Rappemonads and Haptophytes

• haptista are characterised by the haptonema, a third appendage used for attachement and food handling

• three groups:

  • Haptophyte

  • Centrohelida

  • Rappemonads

• predominantly planktonic

• some cells are covered of calcified plates, the coccoliths

• marine environments worldwide

• major component of the marine ecosystem

• play a significant role in the global carbonate cycle through photosynthesis and calcification

• blooms can be seen from space

• the turquise color is a result of the light getting scattered by their calcium carbonate coccoliths (scales)

• diversified in the Mesozoic to become a significant component of the phytoplankton (todays evidence, the white cliffs of Dover)

Supergroup TSAR - the secret rulers of our world

• TSAR: Telonemids, stramenopiles, alveolates, and rhizaria

• it is a gigantic assemblage of eukaryote lineages and possible a rival to Opisthokonta in diversity

• it includes several

  • major groups of microbial algae (e.g. diatoms, dinoflagellates)

  • large seaweeds (e.g. kelp)

  • ecologically important free-living heterotrophic microbial eukaryotes (e.g. ciliates, foraminiferans, radiolarians)

  • many well-studied parasites (e.g. apicomplexans, oomycetes)

Alveolata

• molecular data is supported by a morphological synapomorphy: the cortical alveoli under the cell membrane

• two main subclades:

  • ciliophora (ciliates)

  • Myzozoa (apicomplexa, dinoflagellates, perkinsea)

• evidences of seocndary endosymbiosis:

  • apicomplexa: derived non-photosynthetic plastid called apicomplast

  • cilliates: multiple genes of apparent algal origin present in the macronuclei

• Ciliophora →

  • more than 8000 described species

  • nuclear dualism:

    • micronucleus (2N, “germ line”)

    • macronucleus (> 2N, “somatic line")

  • macronucleus polyploid and undergo direct division without mitosis. It controls the Non-reproductive cell functions, such as metabolism

  • sexual reproduction by conjugation

  • cilia covering most og the cell, sometimes arranged in dense patches (e.g. cirri)

  • perfectly adapted to life in soil/sediments, but also present in the plankton (e.g. tintinnids)

  • all heterotrophic species (kleptoplasty of cryptophytes)

  • form a lorica with debris

  • they feed primarily on other protists and bacteria

  • they are an important part of the fossil record

• Apicomplexa →

  • very succesful group of endoparasites or endocommensals of animals, from corals to humans:

    • COccidiomorphea: contain well known vertebrate parasites like Plasmodium (malaria) and Toxoplasma which means that these aprasites evolved from free living algae

    • gregarinomorphea: contain mostly invertebrate parasites

Dinophyta →

• atypical nucelus (dinokaryon) with high DNA content and permanently condensed chromosomes

• 550 genera with > 2000 species (~50% photosynthetic)

• athecate (naked) or thecate (cellulose cell)

• many cases of plastid loss (and re-aqusition from variuos donors: haptophytes, chlorphytes, cryptophytes by kleptoplastid)

Rhizaria →

• still poorly known genetically compared with other major TSAr clades

• united by molecular and morphological data (amoeboid “tendency” - filopodia and reticulopodia)

• foraminifera - the benthic builders

  • main group with microfossil record

  • more than 12 000 species

  • mostly benthic

  • several live in symbiosis with teh dinoflagellates Symbiodinium (same found in corals)

• radiolaria

  • the favourite protists of artists

  • great carbon sinkers

Stramenopila

• major clade supported by both moelcular and morphological data (falgella with tripartite tubular hair - mastigonemes)

• diatoms and brown algae

• heterotrophic protists

  • including parasites

  • commensals of plants and animals

  • lineages known only from environmental DNA

• Bacillariophyta →

  • the jewels of the sea

  • enclosed in a siliceous frustule

  • heterokont flagella present during sexual reproduction

  • 250 genera, > 10000 species

  • ~20% of the phytoplankton primary