Oyster reefs are in major decline along both the Atlantic and Gulf coasts. This is
important because oyster reefs stabilize shorelines, helping to reduce levels of erosion. Around
6.2 billion oysters live in the Virginia portion of the Chesapeake bay and even this number is
low. Oyster population has been declining from pollution caused by people being irresponsible
and not disposing of their trash correctly, and overharvesting. Both of these have become
serious issues in the past few decades. Being the keystone species of the Chesapeake, the
decline of oysters has caused havoc on the Bay. Keystone species are the animals that let the
ecosystem function at its full potential. With important jobs like purifying water and providing
shelter in the form of oysters reefs, it is no wonder oysters sustain the Chesapeake. Oysters
shells are 95% calcium carbonate which means if the earth run out of this material from mining,
the oysters population will dramatically decline. With our goal of responsible consumption and
production (supporting the strengthening of scientific and technological capabilities to move
towards more sustainable patterns of consumption and production), we can help to ensure our
oysters keep our Bay healthy and clean.
Limestone mining is the primary source of calcium carbonate for the world, and is very
important, especially in Portugal . Calcium carbonate is a crucial material in the production of
thousands of everyday goods ranging from cement to vitamins. This nonrenewable resource is
used in many places, and it is present in great buildings, such as monasteries, or in the famous
Portuguese sidewalk . However, limestone mining has many negative environmental impacts
and is unsustainable; there is a finite amount of limestone on the earth. Mining limestone leads
to the production of high amounts of waste residue which promotes negative environmental and
landscape impacts. These residues are essentially dusts, sludges and discarded mineral mass
in runoff. In addition to this, there are also negative impacts on the quality of the air. Carbon dioxide which is released from mining equipment when limestone is extracted causes global
climate change and causes the water to become acidic which can cause oyster shells to
become brittle. It is important that entities are held accountable to minimize the consequences
of these problems. It should be mentioned that the quarries of Aire and Candeeiros mountain
range got the first position in a list of the ten places identified as environmental black points in
Portugal, which include other quarries, the territory, dams, abandoned mines, coastal erosion
and fires. These harmful environmental effects are able to be reduced if we switch to oyster
framing where oysters are restored after consumption.
Oysters are harvested using nets connected to boats primarily for the reason of human
consumption.This harvesting of oysters has caused their population to decline rapidly which is
why regulations have been put in place in an attempt to protect the oysters. These new rules
limit size and amount of oysters you can take. There are many ways people help but one way is
to increase the number of oyster farms. In this practice oyster are harvested but then new
oysters are “planted back” to the environment. Recycling of used shells can create natural or
artificial reefs like those seen in reef balls.
Oyster reef balls help to regrow the population of oysters in their natural environment.
These reef balls are made of concrete which can be made up of either limestone or reused
crushed oyster shells. One problem with the use of the reef ball is that while they are good for
the environment, they cannot be used in oyster farming because of how much they weigh.
Another option for the rebuilding of the oyster reefs is to use un-crushed empty oyster shells. In
an interview with oyster farmer Kevin Boyle from Shore Thing Shellfish, he stated “ Baby oysters
love to attach themselves to other oyster shelves. So by us reusing oyster shells and putting
them back in the water, instead of the trash, gives new baby oysters a place to attach and
grow.” While un-crushed oyster shells allow for oyster farmers to breed new oyster spat, the oyster reef ball is still the best known option for rebuilding natural oyster population. Oyster reef
balls are a very important for the reconstruction of the global oyster population, and limestone
has the potential to affect oyster reef rebuilding.
There is a definite connection between limestone and oyster reefs. A main chemical
component in limestone is calcium carbonate which is also found in oyster shells. Limestone
runoff seeps into the groundwater and travels to the ocean. Through their filtration system the
oyster takes in water and keeps the nutrients as food and releases the rest of the water out
through gills. The oyster keeps the calcium carbonate in the water from the limestone runoff and
builds a shell out of it. Another example are oyster spat, young oysters, that use a surface to
grow and mature on. According to an experiment from the National Shellfisheries Association,
spat can not cling to a silicon surface nearly as well as a calcium one. Limestone produced and
maintained 2156.5 spat while sandstone, a silicon surface, only produced 338.5 spat under the
same conditions.
However limestone is not only a good surface for maintaining spat but it is used to make
cement because of its chemical makeup. Oyster shells are often wasted and discarded but due
to the calcium carbonate chemical makeup, the oyster shells can be a good substitute for
limestone in the making of cement, as mentioned earlier. The cement can then be used to make
reef balls to increase oyster production to keep up with the amount farmed. This can limit the
amount of discarded and wasted shells and the amount of limestone mined creating a
sustainable replacement for Limestone and increasing the sustainability of oyster farming.


Alunos envolvidos no projeto: Alexandre Pedro; Beatriz Gens; Elizabeth McNiff; Jalena Smith; Johnny Lansdell; Lilian Styles; Zach Zobair

Escola: Externato Cooperativo da Benedita

Data: 06.04.2018

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