Plankton and Junk Food

Plankton and junk food

Hello!

I am in Plymouth at present, working at SAHFOS http://www.sahfos.ac.uk/ to finish analysing some samples I took on the UK-Chile cruise I sailed on in 2010. Wow, finally after almost 2 years I'll be able to figure out what was going on in the ocean when I looked at it. Well... at least answer the little tiny question I asked myself back then. You will probably wonder...what question was it? In a few months I will reveal it all! I just need to finish my thesis first. Let's just say I wanted to find out a little more about how copepod health is affected by what they eat. It's important you know?! Have you seen that "Supersize me" programme? Well...copepods may have an issue with junk food too...

Anyway. What is good about being here is that SAHFOS have the best Plankton taxonomists in the world and the lots of books that can help me with the identification of the copepods I have seen. Also, they have access to fresh plankton every week (for experiments).

Here what they do and why: http://www.westernchannelobservatory.org.uk

As you can see there are plenty of people interested in plankton and all of us look into different things and ask different questions. SAHFOS for example, has been scanning the ocean for a very long time (more than 60 years!) and their ultimate goal is to have a time series of data available to anyone interested showing species distribution over space and time.  This is because plankton responds to environmental changes much quicker than other animals.

Monitoring plankton is beneficial for us all as in the plankton you get larvae of fish and crabs etc..things that we eat and love! I mean, we eat a LOT of fish worldwide. Therefore looking at things such babies abundance and health can help us identifying problems in the fisheries.

For more info on the system they use visit their website! It's a really clever device.


raffles79

Introduction to Plankton - Phytoplankton

In my first "Introduction to Plankton" post I introduced the different types of plankton that live in the ocean. I now would like to expand my introduction and focus on one plankton type at the time. I think the logical way to do it to start from the base of the oceanic food chain upwards (downwards in the picture below in order of appearance in the food web) . 

Oceanic food chain.
Phytoplankton at the base , eaten by zooplankton.

The term "food chain" stands for the representation of what species live in a certain ecosystem (environment) and how they are linked together in a sort of "who eats what" order. Basically all organisms that live in a certain habitat interact with each other, those interaction follow an order which, in simple words, start from the simplest life form upwards. 

Different habitats and ecosystems have evolved throughout time different complexities in their food chains, depending on how many species live there and the environmental factors. Although doesn't matter where, they all have one thing in common, the first link of the chain is plants or so called PHYTOPLANKTON (unicellular algae) in the ocean. 

Because plants and phytoplankton are the first link in the various chains they are called PRIMARY PRODUCERS. Plants can produce their own food through a process called photosynthesis (this is what autotrophs means: plants are autotrophs). The two most important things that phytoplankton needs to do that are:

• light



Phytoplankton growth

• nutrients  (inorganic)

So different light intensities and different nutrient concentrations will determine how well phytoplankton grows and develops. Temperature also plays a major role. Different environments often offer different amounts of the 2 required items. For example, think of polar waters compared to equatorial areas, you will find different species of phytoplankton living in these 2 parts of the world. This is because the 2 areas have completely different characteristics,  therefore the phytoplankton grows differently and over time evolved to adapt to the specific conditions of the habitats. 

Because of this dependence on light, phytoplankton productivity is highest near the surface water and decreases with depth. 

The most important Inorganic nutrients necessary for phytoplankton growth  are CARBON (C), NITROGEN (N) and PHOSPHATE (P) (macronutrients) plus others so called micronutrients such as IRON (Fe). Micro because they are necessary in smaller quantities for the cells to function.

Generally those nutrients are limited at the surface of the open ocean waters with nitrogen and phosphorus in especially short supply; (this is a primary reason for the relatively low productivity of open oceans). Marine phytoplankton is more productive near the coasts were input of nutrients come from the land running off into the surrounding waters. Also productivity is higher in upwelling areas where nutrient rich waters come to the surface.

In one of  the next posts I will talk about the different types of phytoplankton and how to culture it! 

Collecting Plankton

Carboys and Emma

A few weeks ago I went to collect some lovely plankton off the coast of Great Yarmouth. The company were I used to work before (Gardline Environmental), is kindly helping me in my quest for it.

Emma and I went out on one of their fast cats. It was a very clear day and thankfully very calm! I do suffer of seasickness and unfortunately, I am one of the very unlucky ones that really cannot get over it; doesn't matter what I do. But I love the sea so much and I will keep going back.

Emma's version of the event is here:  http://sowhataboutseaweed.wordpress.com/2011/04/11/monday-media-copepod-hunting/

WP2 Bongo net 0.2mm mesh.
AMT20 zooplankton pre-dawn cast

We deployed our nets not too far from the coast in the cold water (8 degrees!) and collected some little zooplankton and copepods for me.

There are different ways of collecting plankton, mainly because it depends on what plankton you want to sample. As I mentioned in my previous post "introduction to plankton", the is quite a variety  of plankton and plankton sizes which can effect the selection of the sampling method. Plants and animals are collected usind different equipment and separately.

I am interested in MESO - zooplankton. This means I want to target animals and in the size range of 0.2-20 mm.

Plankton net cleaning

I also have to consider the environmental conditions of where I want to sample. In the North Sea for example, the water is quite shallow and murky and a little bit colder than in the English Channel. The zooplankton population here tends to be a little bit smaller. For instance, very abundant around here is a copepod species called Temora Longicornis, adult females are about 1mm in length.

The standard way of sampling mesozooplankton is to deploy a 0.2mm mesh sized WP2 plankton net. "WP2" stands for the type of net, it defines the net diameter (usually 57cm) and the proportions of the net. Combining 2 nets together like in the pic to your left makes a "bongo" net.

However I selected a smaller net with a 0.12mm mesh. The picture above shows the little net I used and the  "anatomy" of a plankton net .

We towed the net slowly for a few minutes and then we recovered the sample.  Copepods are delicate and sensitive to light, I need them to stay alive for my experiments so I took a few measures to limit the stress as much as possible. I delicately emptied the cod end into a darkened carboy and made sure the copepods had plenty of water to swim about. Soon I will show you a few pictures of my little ones.

Back at the lab I started sorting them out under the microscope and I set up a culture. They are now reproducing and swimming in my buckets.

Introduction to Plankton

So far I haven't been really talking much about my science in this blog, but It's because I want to introduce things slowly. Today I would like to start from the basics and introduce Plankton. So...what is it?

Several scientific terms are derived either from the Greek or Latin. The word plankton, for example, is from the Greek for "drifters". It is because those things that are called plankton are very small and therefore not strong enough to actively move against underwater currents. Although some can move up and down (vertically) in the water column, others cannot move at all and just....drift. 

There are different types of plankton, classified depending on their size but also depending on their functional groups. The latter means that plant, animals and bacteria that are considered "planktonic" have different names.

• Phytoplankton: unicellular plants (they are photosynthetic). Phyto is from the Greek for plant.
• Zooplankton: animals (they eat other zooplankton and phytoplankton). Zoo is from the Greek for animal.
• Ichthyoplankton: eggs and larvae of fish. They are temporary plankton, once they reach adulthood they become NEKTON - free swimming animals that move independent of water motion. Ichthyo is from the Greek for fish.
• Bacterioplankton: bacterias (they live everywhere!). 

Here a quick sketch to show you what I mean (not to scale!!!)

Plankton sketch (not to scale)

Plankton. From: http://www.duke.edu/web/nicholas/bio217/jrc25/impacts.html

The size classification is based on certain metric ranges and it can be independent of the type of plankton, like this:

Mega-plankton          20+ mm                    e.g. Jellyfish

Macro-plankton         2mm - 20mm          

Meso-plankton          0.2mm - 2mm           e.g. larger copepods

Micro-plankton         20µm - 200µm        e.g. most phytoplankton

Nano-plankton          2-20 µm                    

Pico-plankton            0.2-2 µm                e.g. bacteria & small phyto

Femto-plankton        < 0.2 µm                    e.g. viruses

PS: µm is called micro-metre

You can be a little more precise if you want and take it a step further combining the plankton type with the size, like this:

Meso-zoo-plankton

Pico-phyto-plankton

Not all the combinations can make sense thought! As you can see the  biodiversity in the world of plankton is enormous. My areas of interest are mesozooplankton and phytoplankton.

Why do we study plankton?

From http://www.sahfos.ac.uk/research/research-home.aspx

Plankton as indicators of the health of the oceans

At the base of the marine foodweb, the free floating plant life of the sea (phytoplankton) provide food for the animal plankton (zooplankton) which in turn provide food for many other marine organisms. The carrying capacity of marine ecosystems in terms of the size of fish resources and recruitment to individual stocks as well as the abundance of marine wildlife (e.g. seabirds and marine mammals) is highly dependent on variations in the abundance, timing and composition of the plankton.

These organisms also play a crucial role in climate change through the export of the important greenhouse gas CO2 to the deep ocean by carbon sequestration in what is known as the 'biological pump'. Without this process concentrations of CO2 would be much higher in the atmosphere and the climate of the world would be much warmer. Apart from playing a fundamental role in the earth's climate system and in marine foodwebs, plankton are also highly sensitive indicators of environmental change and provide essential information on the 'ecological health' of our seas.

Grow Plankton

Hello,

It has been a while! I must apologize. I have been so busy I had no time to do anything. Busy doing what you may ask...erm...work! The most important experiments of my PhD career have started. I have set up 3 phytoplankton "continuous" cultures (in the pic) and I am now waiting for them to reach a "steady state".

My continuous cultures

Ok I think a brief explanation is in order. Well, phytoplankton are the little unicellular plants that live and drift in the ocean. There are many different species, of a variety of colours and sizes:

Batch cultures I grow to feed zooplankton

What they need to survive (like any plant), is light and nutrients dissolved in the water. The main nutrients they survive on are Carbon (C), Nitrogen (N) and Phosphorous (P) [Iron (Fe) too but in minor quantities].

We grow different species in the lab and in order to do that we have to make some nice nutritious seawater for them, full of those nutrients they like as well  as vitamins and minerals. It's a bit like cooking, just mixing powders and/or solutions with strange names all in a bottle.

Anyway, if you grow them in a closed bottle, the little ones will go on absorbing all the nutrients in the water until they run out. Which means they will eventually die. That is called growth curve:

http://microvet.arizona.edu/Courses/MIC205/Exams/05Exams/05Ex2key.htm
It says bacterias on the side but the principle applies to phytoplankton too (over DAYS not hours).

So...to keep them in the so called stationary phase I started to grow them in a "chemostat" or a continuous culture, where they receive daily rations of nutrients to keep them alive and going for a long time in a state of equilibrium (until the big carboy runs out of media that is). 

I must confess, set one of those things up is not that easy, there are a lot of things that go wrong all the time and the stress levels riseeeeeee. Every day there is something new to sort out...one day I will get it perfect! 

They are so colourful, nature is amazing.