OceanMOOC | 10.2 | Ecosystem and Nutrient Management

OceanMOOC | 10.2 | Ecosystem and Nutrient Management


In this lecture I will present you with a
positive example of marine management here with nutrient management in a semi-enclosed
sea, the Baltic Sea. You will learn that it’s essential that coastal management is working,
that there are effective international treaties so that nations work together that are situated
around or along a coastline. You will see that sound scientific analysis of the problem
is essential to find the right solution and you will see that many management problems
towards sustainable use of oceans are multi-factorial problems, so there’s no single patent solution
that will bring us forward, but a bundle of solutions that we need in this case, to find…to
fight nutrient pollution. Nutrient pollution is a very serious threat
to many ecosystems, in particular, along the coasts. For one thing they cause algal blooms,
for example here blooms of blue-green algae that can be toxic and when they die and sink
down, they will cause oxygen depletion or oxygen dead zones. And also nutrient pollution
may kill coastal vegetation by overgrown with ephemeral opportunistic algae.
So these problems of nutrient pollution are still relatively benign in open ocean areas.
But they very much affect coastal areas and they are extremely critical in enclosed oceans
such as the Baltic Sea, that is surrounded by 80 million people that are living in industrialized
countries with a pretty intense agriculture and other lifestyles we will see in a minute
that all produce mineral nutrients that enhance plant growth in the sea. The Baltic Sea is
the largest brackish water area in the world and it’s surrounded by several countries,
most of them are E.U., European Union member states. And that’s going to become important
for the governance aspect of the nutrient management.
So how severe is the situation in the Baltic Sea? It’s pretty severe. And the, the Baltic
is actually a bad case study of some of the most extensive dead zones that are not even
with low oxygen levels as here depicted in red, but that have zero oxygen and the development
of hydrogen sulfide that’s toxic to most animals.
And those dead zones we now know through very good time series from sediment cores, they
have expanded twenty-fold in the past 100 years.
A sound scientific analysis of the nutrient influx situation revealed that there are several
different critical sources of nutrients. So we have point sources, those are relatively
easy to deal with, so they are mainly wastewater from municipal settlements and they can be
dealt with by setting up wastewater treatment plants and this has happened in the past 20
years in a very ambitious program all around the Baltic.
However, those point sources often only contribute to 50% or less of the total additional nutrient
influx into the Baltic Sea. The bigger chunk are diffuse sources from, mainly from agriculture
practices and from traffic. You may be surprised here. And those diffusive sources, they either
come through rivers or even through the atmosphere. And how would traffic be contributing to fertilization
here by nitrogen species? So this is because the combustion of gasoline produces different
nitrogen oxides, collectively called NOX. And when they rain down, they are perfect
nitrogen fertilizers. So here we see very nicely the interdependency of many environmental
problems. You may not have thought that every culture practices, including organic farming
way inland may affect the nutrient balance and ecosystem health in an ocean. And likewise,
you probably may not have thought that having appropriate catalytic converters in cars that
will convert the NOX to N2 that’s inert and that’s just what we breathe in 80% of
every breath we take would again help to alleviate nutrient pollution in the Baltic Sea.
So collectively changes in agricultural practices, for example, better timing of manure, protecting
the watersheds, leaving a strip of land not used for fertilization and also of course
implementing clean air, better catalysts in cars, collectively led to a decrease in the
estimated input of nitrogen into the Baltic and the same would hold for phosphorous, the
second major micronutrient element. But there can be more to nutrient management
and that’s currently been under intense research. So one more innovative measure may
be to expand mariculture with rope culture of mussels for example to actively extract
nutrients in the form of the biomass then of the mussels, which at the same time would
provide biomass from the oceans that can be converted into animal food for example and
the same would be true with algal culture. And also again, in a more integrative perspective,
we also have to look at the natural coastal vegetation that’s able to absorb nutrients,
that’s a critical and very valuable ecosystem service that macrophytes such as sea grasses
in the Baltic Sea, but also bladderwreck as a major algal species provide for humans.
So they absorb nutrients into their biomass and they store it for a longer term.
So those two innovative measures, mariculture and enhancing the coastal vegetation are some
additional, not exclusive, but additional measures where there’s intense research
at the moment how much they could contribute to even make the nutrient balance for the
Baltic better. So what was critical to make all of this happen?
I think very critical is if we look how the ecosystem health in the Baltic is working
in terms of governance structures. Most of the Baltic countries except Russia are EU
member states now. And the EU has set quite ambitious goals of achieving a good environmental
status by 2020. And there’s also, there would be a financial punishment if those goals
are not achieved by the EU commission. And at the same time now, even taking Russia
on board with the HELCOM commission, there has been the Baltic Action Plan which basically
enforces that legal body implemented by the EU. Again, towards a management of this coastal
ocean and here very specifically to reduce one of the most severe environmental problems,
that is, nutrient pollution. So take home message is governance here is
essential. If you have many countries sitting around an ocean or along a coastline that
has to be dealt with as one management unit, they have to cooperate. They have to work
together. And they have to set. And they have to set specific goals here for example for
nutrient reduction, otherwise it would not work.

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