Project Synopsis: Particle impact on Ocean Omnivory and Processing (POOP)

A long-term goal of marine biogeochemical studies is to understand the processes involved in biological carbon sequestration in the ocean. Predicting the future course of atmospheric carbon dioxide (CO2) increases in response to anthropogenic emissions requires a complete understanding of all factors that govern the carbon cycle. A major sink of CO2 is the ocean “biological pump” – a term used to describe the transfer of carbon to the deep ocean for long term storage. Carbon is removed from the atmosphere via photosynthesis by phytoplankton, and ultimately ends up in the deep ocean as sinking organic matter. 

Some of the carbon-containing organic matter that sinks to the deep ocean is found in the fecal pellets of zooplankton, especially copepods. By most estimates, copepods are the most abundant animal on the planet by weight. They feed upon sharp and spiky phytoplankton, including glass-walled diatoms, so their fecal pellets have a strong membrane for a more comfortable exit. Compared to those of other organisms, copepod fecal pellets are fairly dense, hydrodynamic, and resistant to bacterial composition. Thus they sink to bottom of ocean faster, bringing plenty of carbon down with them.

I am investigating the impact of atmospheric dust deposition on the feeding and digestion processes of zooplankton, and its implications for the biological pump. 

It has been suggested that dust can increase the efficiency of the biological pump through various physical and chemical means. Dust is known to be a source of limiting nutrients and minerals to the ocean, and has shown to affect the responses of phytoplankton. However, we ultimately haven't been able to figure out the specifics of how this all works, and how to predict just how much carbon will sink.

So for my project, I am asking: what about the zooplankton, who eat the phytoplankton? How does dust deposition affect their digestion processes, and ultimately the amount of carbon sent to the ocean floor for long-term burial (via their poop)?

Our lab did some preliminary feeding experiments which yielded some very interesting results. Zooplankton were given different feeding solutions: some with only phytoplankton, and some had local dust mixed in as well. The zooplankton who ate the "dusty" solutions were eating a whole lot faster than those without dust... and they were producing more fecal pellets that had more carbon inside them.

It seems that dust particles act as "roughage" inside zooplankton guts: Food passes through them faster without being digested as efficiently. Reduced digestion means more of the carbon they consume remains trapped inside their fecal pellets, which will eventually sink to the deep ocean. On top of that, minerals in the dust make zooplankton fecal pellets bigger and denser, so they sink faster.

We are thinking that the presence of dust can result in the production of more fecal pellets, which sink faster, and contain greater amounts of carbon.... thus increasing the efficiency of the biological pump. 

Dust itself is sensitive to climate, so it's important that we understand this feedback mechanism. 

In the summertime, the Gulf of Aqaba is an oligotropic (nutrient-deplete) environment with a high dust input. Dust storms occur year round, with maximum inputs in late spring. This summer I will deploy sediment traps in the Gulf of Aqaba in time series and access archived samples from periods of variable dust deposition. I will also run zooplankton feeding experiments in seawater tanks at both the Gulf of Aqaba and the Mediterranean Sea. At IUI, I will collect and analyze zooplankton fecal pellets from both trap samples as well as the experiments.

Results will be compared with similar experiments conducted back in California, as well as data from fecal pellets collected from sediment trap archives across the world. Research will provide a wide range of results relevant to many disciplines. No quantitative or mechanistic understanding for these relations is currently available, and data documenting the process is limited. Investigation of this interaction will help improve our model of the ocean carbon cycle, and our understanding of carbon sequestration via the biological pump. 

Project Synopsis: The Ecological Effects of Desalination Brine

I wonder, how many of you reading this had ever considered drinking seawater? When I was a kid playing at the beach in summer times, my parents always told me not to drink the seawater; It would make me sick. In many parts of the world, ex. Denmark where I grew up, drinking water comes from the ground as groundwater, from rain, lakes, rives, aquifers or other terrestrial sources - not from the salty Ocean.
However, in other parts of the world, groundwater is extremely scarce and rain almost non-existing. How does people get drinking water in these regions? Well, one way is actually to drink the Ocean. Of cause not literally taking a glass down to the beach and pour in some water - but take the seawater and treat it; remove the salt; desalinate it.
The Ocean covers more than 70% of our globe and consists of almost 90% of all accessible water. Using this massive water resource for drinking water seems almost too logical.


Desalination of seawater is a widely used source of potable water in arid and semi-arid regions, like the Arabian Peninsula, Israel, parts of the Mediterranean region and now in drought-stricken California too.

The process of desalination can be described very simplified: Seawater is pumped into a desalination plants where, by various methods, the salt is removed and the water cleaned to make fresh drinking water. Many desalination plants are using reverse-osmosis to remove the salt from the water. In this method, pressure is applied to push the water through a semi-permeable membrane creating two products: fresh water and a high-salinity brine. The brine, along with various chemicals used for treatment and cleaning at the plant, is then discharge back into the ocean, very often in close proximity to shorelines and beaches.

Schematic diagram of the SWRO process

Despite the growing popularity of seawater reverse osmosis (SWRO) plants and the overall global interest in seawater desalination, very little is know about the consequences of discharging brine into coastal communities.

The addition of very saline water in a confined coastal area could cause changes in the biochemistry and biology potentially leading to changes in the trophic levels, coastal pollution or recreational disruption.


I study the effects of such brine in coastal areas. My main focus is the ecological effects on ocean organisms and I hope to be able to identify what happens in the coastal zone when discharging brine, which constituents in the brine is effecting organisms and the boundary limits and thereby help to increase the sustainability of seawater desalination.

During my time in Israel I will conduct two biological experiments, that hopefully will enlighten how different organisms will respond to brine discharge.

Phytoplankton growth

Firstly, I will look at how phytoplankton will respond in their growth, primary production and the structure of the community, eg. what species of phytoplankton is growing.
Phytoplankton make up the very bottom of the food chain, and changes in their growth and community could cause changes up through the higher trophic levels. Certain conditions can also favor certain phytoplankton species causing periodical blooms of plankton that can, depending on the species, be harmful for both fish, marine mammals and anthropogenic activities.
To test the effects of brine on phytoplankton, I will have to grow them under conditions I control and in a confined space I can access.
The method of choice is to add different treatments to bottles of seawater. The seawater will be collected directly from the ocean surface and will contain a random selection of the local phytoplankton community. The bottles containing seawater will then be treated different ways:

The first bottle will serve as control and have nothing added to the seawater. This bottle is the reference point. The second bottle will have added 1% brine, which will represent the lower margin of what can be assumed to be mixed in the coastal water. The third bottle will have 10% brine, which is representing a maximum concentration of brine. And a fourth bottle will contain some of the known chemicals and metals discharged along with the brine.
Over a period of 5 days the bottled and treated seawater will be monitored and by the end it will be possible to map out how the phytoplankton grew in the four different conditions.

Four bottles containing seawater and each a different treatment.

Coral health and growth

Secondly: I will be looking at coral health and growth in brine.
Corals are, to many, pristine ocean creatures and some of the most diverse and lively reefs are located in the Red Sea - many in close proximity to desalination discharge.
Coral reefs are crucial habitats, shelters and feeding grounds for enormous amounts of fish and seacreatues and are recreational havens for scuba divers and snorklers providing and important economic factor for the countries with coastal coral reefs.
The health and well-being of coral reefs are therefore important in many aspects.
In a similar manner as with the plankton, I will grow corals under specific conditions and monitor them. To do this, small fragments of corals has to be collected from the ocean. The fragments are collected from specific coral nurseries, that are artificial reefs in the ocean, where corals are grown with the specific purpose of using them in science experiments. This enables scientists to do research on corals without disturbing actual reefs.

For the corals a control and a 10% brine treatment will be monitored. Because of the much slower growth, this experiment will be running for a minimum of 4 weeks. Each week a coral fragment will be collected and it will be analyzed for its growth and for the growth of the symbiotic algae living within it.

Schematic of an aquarium with coral fragments growing in it

I am excited to get started on these experiments and see what will happen when, under controlled conditions, local species are introduced to a higher salinity.

Stay tuned the next two months for updates and pictures of the bottle incubations and aquariums full of corals!

Project Synopsis: The Health of Red Sea Giant Clams

Picture of T. squamosa. The colors in the "lips" are produced by the photosynthetic pigments of the clam's symbionts. From Wikipedia.

The Northern Red Sea is a unique place to study coral reef ecosystems. I am traveling there this summer not to study reef-building corals, however, but instead will focus on a different group of massive reef inhabitants: the giant clams (genus Tridacna). The three species of giant clams in the area represent the northernmost known population of the genus in the world. I intend to compare the growth of fossil and modern populations to determine whether their modern growth is inhibited relative to their ancient counterparts, and whether that decline is due to human pollution and influence on their environment.

Giant clams grow to huge sizes with the help of symbiotic algae that live within their tissue. The algae get nutrients and a safe environment while the clams are free to harvest the sugars produced by photosynthesis, allowing them to hypercalcify and build massive, thick shells at a rapid rate. The three species of the Red Sea vary in their degree of reliance on these symbionts as opposed to the filter feeding which they also use for some nutrition. The most photosynthetic species, T. squamosina, is also the most threatened. It is only able to live at the reef top, where it has access to sunlight but is also vulnerable to human over-harvesting. Shells are highly sought after as souvenirs, which has severely impacted populations of giant clams around the world.

T. squamosina shell from California Academy of Science Collection. Photo by Dan Killam.

I hypothesize that the giant clams of the region are also impacted by pollution from agricultural runoff, fish farming and urban sewage outflow. All of these factors reduce water clarity and promote algal blooms, which reduce the photosynthetic rate of the symbiotic algae that the clams rely on. I propose that this distinction is what has caused T. squamosina to lose most of its population. Previous studies have shown that it was over 80% of pre-human fossil assemblages, but it is now reduced to a small remnant population.

To test this idea, I will be collecting fossil clam shells and comparing their shells to modern individuals obtained from the beach at the Eilat Coral Reserve. These shells can be cut to observe internal growth bands, which are a record of the rate of growth, length of life and metabolism of the organism throughout its lifespan. If clams in the past grew faster, they should have wider bands on average. If longevity was longer, they should have more total bands across their shells. The carbonate of each band is a record of the local environment at the time. If clams were subject to different temperatures, we will be able to see that signal in the oxygen isotopes of their shells. Lastly, we intend to extract amino acids protected within the shell crystals to determine whether the clams' tissue makeup has been impacted by human-sourced nitrogen from fertilizers and sewage. If we find that slow-growing, short-lived clams predominantly seem to be influenced by human pollution, we will have created a link between the suppression of their growth and pollution, which is valuable information to explain their decline in this region.

I am a paleobiologist and a conservationist, and so hope that being able to compare long-dead and more recently dead individuals of these amazing organisms will help us understand what must be done to protect and increase their populations in the future.

A New Chapter Begins...

The 2016 class of Coastal IRES is currently deep in work planning for our upcoming expedition to Eilat! There are three student participants this year, including oceanographers Michele Markowitz and Karen Petersen and paleontologist Dan Killam. We have diverse fields of study but are united by an interest in dynamics influencing the environment of the Israeli coast. Michele is investigating the influence of dust deposition on the efficiency of the biological pump, a mechanism which is an important control on deep ocean storage for the global carbon cycle. Karen is monitoring how brine discharge sourced from Israeli desalination plants affects the local phytoplankton and coral ecology of the region. Dan is researching how the giant clams vary in growth rate and metabolic health between ancient and modern times, and whether pollution depresses their growth rates.

Each project is described in more detail on the "Research Participants" page, and we will each be contributing a post outlining what we intend to achieve during our fieldwork this summer. We will also be narrating our experiences with day-to-day data collection, analysis and our general experience in the country of Israel. Our journey begins July 1st. Stay tuned!