Nuclear Energy

Nuclear energy harnesses the power of the atom to generate tremendous amounts of electricity
from a very small amount or fuel. This controversial source is non-renewable because there is a
finite amount of uranium, and while it produces no carbon emissions it is not “green” because of
the radioactive waste it produces.

Nuclear power plants use the heat created by splitting uranium atoms to create steam either by
boiling water or turning pressurized water into steam without boiling it. The steam turns turbines,
which generate electricity. In both boiling water and pressurized water systems the steam is
condensed back into water to be cycled again. 

Nuclear fission in action

Much of the controversy surrounding nuclear energy is a fear of what could happen. In the years
since nuclear energy plants began generating, there have been three major accidents- Three Mile
Island in 1979, Chernobyl in 1986, and Fukushima Daiichi in 2011. An example of what could go
wrong follows.

Three Mile Island was a loss of coolant accident. A mechanical failure prevented water from
reaching the reactor core to cool it. As pressure began to build in the core, a relief valve opened
as it should have, but remained stuck open when pressure returned to normal levels. Cooling
water poured out of the valve, but plant staff was unaware as instruments indicated the valve was
closed. Without correct information from instrument readings, staff incorrectly reduced the amount
of cooling water going to the reactor, which caused it to overheat. The zirconium cladding that
contained the uranium fuel pellets began to melt. A hydrogen bubble formed inside the containment
dome, raising fears of an explosion and containment breach. Pregnant women and small children
were ordered to evacuate, and there was a release of radiation (done intentionally to relieve pressure)
but not enough to cause any health issues. Plant staff resumed the flow of cooling water and were
able to reduce the hydrogen bubble. The reactor stabilized, and it was discovered that about half
of the core had melted. 

Three Mile Island. The cooling towers for the damaged
reactor are in the foreground. (Lancaster Online)

Safety has improved considerably at US plants. In fact, the costs associated with safety, security,
and permitting have become almost prohibitive to opening new plants. A plant in Tennessee will
be coming online in late 2016, over 40 years after construction began because low demand for
electricity and did not justify the cost of completing the plant until recently.

Aside from safety concerns, spent nuclear fuel is an issue no one is quite sure how to deal with.
Currently, spent nuclear fuel is stored on-site at power plants. First, it is stored in a cooling pool
for a minimum of five years. When it has cooled enough, it is encased in a concrete and steel cask.
However, the material will remain radioactive for thousands of years and a permanent location for
disposal has yet to be found. Reprocessing allows uranium and the resulting plutonium to be reused
as fuel, which cuts down on the amount of waste material but only delays the problem.

Spent nuclear fuel in a cooling pool (International Atomic Energy Agency)

One potential solution to the waste problem is transatomic power, which dissolves nuclear waste
into molten salt, would reduce the amount of spent nuclear fuel by using it again. It also has the
potential to reduce the half-life of waste, or amount of time that it takes for half of the mass to decay
and no longer be radioactive.

Another negative environmental impact of nuclear energy is the potential for radioactive release or
water pollution from tailings at uranium mines. Uranium tailings are radioactive, and may contain
sulfides that can produce acids. Tailings should be placed within an engineered dam and then back
inside the mine when operations conclude (World Nuclear Association, 2013).

After examining various methods of energy production, it has become clear that no source is
completely free of environmental impacts. The negative impacts are wide ranging, from localized
to single windmill to a global scale with fossil fuels. Fossil fuels have been widely panned for the
environmental damage they cause at a regional level for oil spills to the global climate change
linked to carbon dioxide emissions. They have been ruled out as the “greenest” energy, but what
about the others? 

Wind, solar, tidal, and geothermal appear to have the least negative environmental impacts but
can be limited by factors such as geology, topography, and weather. As technology advances, it
may be able to overcome these limitations. An ideal solution to the fossil fuel problem is to
increase their generating capacity and incorporate them into an improved and more efficient grid.
Since these sources, as well as hydroelectric, are mainly regional a better grid would blend all
electricity into a single network that can easily transfer energy to rapidly meet demand. Thus,
hydroelectric from the Pacific Northwest could supply power to Iowa when the wind stops blowing. 

So what is the “greenest” energy? It is all a matter of personal preference and an individual’s
tolerance for the different negative impacts. Bird strikes from wind energy may be a more pressing
concern for some people than fish strikes caused by tidal energy. 

This week's information comes from Duke Energy, Nuclear Regulatory Agency, Wired, Nuclear Regulatory Commission, Transatomic Power, and World Nuclear Association.

Tidal Energy

Continuing the series on alternative energy sources, this week features tidal energy. It is similar to
hydroelectric power: it uses the same principles of water in motion and is also a “clean” energy source.
However, tidal power relies not on the temperamental flow of a river which is subject to effects of
weather and climate but on the timeless and ceaseless pull of the sun and moon on the world’s oceans.
Because of its reliance on ocean tides, this is considered a renewable energy source because it does
not diminish the amount of tides in the ocean.

Tidal power is also similar to wind power. Tidal turbines look like miniature underwater windmills.
Tidal turbines can be smaller and more densely spaced than windmills because water is denser than air;
less surface area is required to generate a comparable amount of electricity. While the wind may not
always blow, the tides are always in motion. 

Tide turbines (Forbes)

Another device to harness the energy of the tides is called a barrage. It is similar to a small submerged
dam that blocks the incoming and outgoing tides at the mouth of an estuary. A sluice in the dam opens
to collect the tidewater, which flows though and turns turbines to generate electricity.

One drawback of tidal energy is the tides themselves. Generation capacity is limited by the tidal cycle,
meaning peak demand will frequently be missed. Also, the change in tides must be at least seven
meters for this to be economically efficient. 

Barrages are limited by location. Not all estuaries are suitable sites. The equipment used for generation (either barrages or tide turbines) must be highly durable due to the unforgiving nature of the undersea environment.

Tidal barrage (Britannica)

Like the other energy sources previously mentioned, tidal power has negative impacts on the environment. However, due to limit use of this technology, these impacts are still being studied and at present are not certain to be occurring. The possible impacts include altered waves, currents, substrate, and sediment movement; loss of habitat for benthic organisms; noise that may interfere with biosonar; generation of magnetic fields; introduction of toxins in paint, lubricants, and antifouling; hindrance of fish passage; and fish being struck by blades or sucked into turbines.

This week's information comes from Marine Current Turbines, Ocean Energy Council, and Pacific Marine Energy Center. After a brief break for a look at June's Species of the Month, this series will resume with wind energy.

Pros and Cons of Hydroelectric

Hydroelectric power generates the most electricity of all renewable energy sources in the US, about
7% of the total production. It is a truly renewable source as the same water can flow through a series of dams on a single river, and it is renewable. It is also “clean”, producing no carbon emissions outside of those during the dam building process. 

Water held back by a dam goes through an intake pipe and turns turbines as it passes through the dam.
Faster flowing water will produce more power. Hydroelectric power is about 90% efficient, making it a
great source of power. Due to controls at the dam, the flow of water can be adjusted to meet peak
demands much more quickly than at a nuclear or coal-fired plant. Some dams are equipped with a
pump and can pump water to a higher level during times of low energy usage. The water is then
released back through the dam at peak times to generate additional power.

Not all dams are generating stations, but hydroelectric dams often serve other purposes such as flood
control, irrigation, drinking water supply, and recreation. Because the water is naturally occurring and
free, hydroelectric power is among the cheapest on the market, less than a penny per kilowatt hour on
average. An electric utility can earn additional income through recreational fees, keeping utility rates
low.

Hydroelectric dam in Arizona (USGS)

Although hydroelectric power is “clean”, it is not completely “green”. Like the fossil fuels, it also has
negative environmental impacts. Dams affect fish migration, hydrology, and sediment and nutrient
movement. Flooding a reservoir also causes terrestrial habitat loss, which is traded for aquatic habitat.

Fish ladders can be built to aid anadromous fish in passing around a dam. These fish hatch in
freshwater, live as adults at sea, and return to their native streams to spawn. The journey through
natural aquatic habit frequently involves jumping over small waterfalls, which fish ladders mimic.
Different species of fish move at different speeds and therefore have different needs. Fish ladders come
in many different designs, and some even look like a natural stream rather than a flooded staircase.
Intake screens covering the intake pipes can successfully keep most fish from getting sucked into the
turbines, which can kill them.

Fish ladder (Army Corps of Engineers)

Terrestrial habitat is lost at the expense of aquatic habitat gain. However, the reservoir behind the dam
is of lower quality than a natural lake and alters downstream hydrology. Reservoir water stagnates
since there is no outlet and sediments and nutrients from upstream collect behind the dam rather than
enriching downstream areas. Downstream ecosystems can also suffer if not enough water is released
from the dam.

Sediment deposits after a dam removal in Washington (NPS)

This week's information comes from US Bureau of Reclamation, Michigan DNR, and
Union of Concerned Scientists.

Herring Spawning

One of the great spectacles in North American wildlife watching is the Pacific herring spawning. It happens every year in late winter and early spring. Not only does the event produce the next generation of an important fish species, it also sustains the current generation of many other animals.

Pacific herring form an important strand in the food web. They are classified as forage fish, meaning they serve as meals for larger fish like salmon. As we'll see a little later, herrings feed the larger community beyond just the salmon.

Herring spawning turns the sea white (Prince William Sound Conservation Center) 

Herring move to shallower seas during spring, which happens to be right around the same time hungry humpback whales arrive from the tropics. The herring are looking for eelgrass or kelp beds for their sticky eggs to attach to. After the females lay their eggs over the vegetation, the males swim over and release their milt to fertilize the eggs.

Before reaching the spawning beds, the herring must navigate a maze of predators: sea lions, sea birds like cormorants and gulls, bald eagles, and those hungry, hungry humpbacks. Once the work is done, the eggs aren't safe and the smorgasbord continues as diving ducks pick them off. About two weeks later, the remaining eggs hatch and the herring larvae are carried by the tide and are subject to predation by fish of all shapes and sizes.

Herring eggs attached to kelp (US Geologic Survey)

With all that eating going on, it's a wonder any herring survive to adulthood. Females typically lay 20,000 eggs a year, and if she lives a long life, she'll do this three times. Multiply her by a million of her closest friends, and you have about 20 billion eggs. If only 1% hatch, that's 200 million baby herring.

Sea lions await their feast (Tillamook Coast)

In a good year, spawning herring will color the sea white. However, the spawning isn't nearly as good as it used to be. Overfishing is one reason, but loss of habitat (spawning and feeding areas) and pollution are also big contributors.
This week's information comes from Wayne Hoffman, Ph.D. and Washington Department of Natural Resources.
nm1: Prince William Sound Conservation Center https://pwssc.org/herring-spawn/
nm2: USGS https://www.usgs.gov/media/images/pacific-herring-eggs-macrophytes
nm3: Wayne Hoffman https://tillamookcoast.com/blog/spawning-of-pacific-herring/

Amazing Okavango

Ever hear of the Okavango River in Africa? You probably haven't. It's a rare river that flows into an inland delta rather than the ocean. During the winter, it floods the glassland and creates a seasonal wetland that attracts wildlife from all over Africa in one of the world's greatest migrations. It is an amazing oasis in the Kalahari Desert.

Flooded Okavango (Natural World Safaris)

The annual flood occurs at the height of Botswana's dry season, so it offers welcome relief to the plants and animals in the area, in addition to welcoming migratory animals of all shapes and sizes. The abundance of water boosts the growth of plants, drawing in herbivores. The herbivores attract large predators.

Elephants (Royist)

Safari cruise through the grasslands (National Geographic)

Among the many different animals who take advantage of the situation are elephants, lions, cheetahs, zebras, rhinos, 89 fish species, and 24 globally threatened birds. Not only is the Okavango key to survival of individual animals, it is crucial habitat for entire species.

Lion and buffalo (National Geographic)

A safari in the Okavango is like watching "The Lion King" live and in person. This weeks information comes from UNESCO World Heritage.

Species of the Month

Shark Week is nigh upon us and we're getting in on it with July's Species of the Month. I've chosen the most famous (or infamous) sea creature, the great white shark. While they've been known to attack people, we are not their prey. Shark attacks may be curiosity or just a case of mistaken identity. Unlike Jaws, these apex predators won't eat you, even if they do happen to bite. Sink your teeth into this quick profile!

Scientific name: Carcharodon carcharias

Great white shark (NOAA)

Kingdom: Animalia (animals)

Class: Chondrichthyes (rays and sharks)
Order: Lamniformes (mackerel sharks) 

Range: Coastal ocean areas of Asia, Australia, Oceana, North and South America, Africa, and Europe

(NOAA)

Habitat: Marine
Lifespan: 30 to 40 years
Diet: Fish, seals, sea lions, sea birds, squid, sea turtles, dolphins, whale carcasses, rays
Predators: Humans, killer whales, other sharks
Conservation Status: IUCN consideres great whites to be vulnerable, protected in the US

(NOAA)

Other information: This massive apex predator can grow to lengths of 20 feet and weigh as much as 6600 pounds! It's mouth can open to over three feet wide, plenty of room for anything it wants to eat. And that mouth is packed with razor sharp teeth. Unlike humans, gifted with two sets of teeth, the great white can apparently grow an unlimited number, replacing teeth as needed. The shark's streamlined body is built for speed and power. Not much is known about their reproductive habits. Females give birth to live young, which eat unfertilized eggs and possibly even siblings in the womb. They are mostly solitary creatures, but sometimes congregate to feed, such as at a whale carcass. In situations like this, they form social hierarchies. In addition to a well-developed sense of smell, great whites can detect electrical fields. These highly developed sense allow them to detect prey by a single drop of blood in 100 liters of water, or by the beating of its heart. The great white's prefer hunting method is to strike from below. A powerful blow is enough to stun the prey, avoiding a chase or a struggle. Across the board, fish populations are declining at an alarming rate and the great white is no exception. Sport fishing, commercial fishing bycatch, and finning take a toll, and as a large species reproductive rates are generally low. As an apex predator, populations are already low to begin with. Sadly, despite its deadly reputation the great white shark has more to fear from us than we from it.
This month's information comes from the University of Michigan's Animal Diversity Web.
nm1 https://swfsc.noaa.gov/textblock.aspx?ParentMenuId=123&id=21434
nm2 https://sos.noaa.gov/datasets/marine-migration-great-white-shark-3d/
nm3 https://oceanexplorer.noaa.gov/explorations/18whitesharkcafe/welcome.html

Reef Madness

Last week we explored the dynamic barrier islands, a great place for wildlife and a popular vacation destination. This week, we venture beyond the island into the coral reefs just offshore. As an avowed landlubber, I'll probably never get to see a coral reef for myself, but I'll live vicariously through myself telling you all about them.

Coral reef (Smithsonian)

Coral reefs are hard, rocky structures made of the skeletal remains of what was once living coral. Corals are a marine animal, not a plant, and the best-known form a symbiotic relationship with algae. Because algae needs sunlight for photosynthesis, many coral reefs are found in clear, shallow water. Cold water corals that live in the deep sea. Without sunlight, these organisms filter feed plankton. Because of their inaccessibility, we are still learning about them.

Coral polyps (NPS)

The most popular corals are the shallow ones, because they are relatively easy to reach. Scuba diving, snorkeling, and even glass bottomed boats bring humans right to the biological hot spots. People are drawn to coral, not just because of the beauty of the coral itself, but the amazing biodiversity found within the reef. Fishes, crustaceans, sponges, anemones, and countless other sea creatures call the reef home. The coral structure provides hiding places for mobile critters and anchorages for sessile ones. Hiding places benefit predator and prey alike- they provide somewhere to hide from bigger fish, or place to launch a quick strike at an unsuspecting meal.

Coral reef (NPS)

Cold water corals provide the same habitat and ecosystem, and may be even more important than their shallower counterparts. Most sea life can be found near the coast and relatively shallow. Corals in the deep sea for a sort of island in an area that is otherwise mostly devoid of life.

Deep sea cold water coral (Joint Nature Conservation Committee)

Like just about every ecosystem in the world, coral reefs are in trouble. Coral is dying as sea temperatures and carbonic acid levels rise. The algae component of the coral either dies or evacuates in a process known as coral bleaching. Some corals show some resistance to slightly warmer temperatures. Research into this is continuing. If you ever get a chance to explore coral reefs, either by boat or underwater, remember to look but don't touch.
This week's information comes from NOAA and the Smithsonian Institute.

Getaway Islands

Summer is here and for many people it's the perfect time to relax at the beach. If you're at an East Coast beach, odds are you're on a barrier island. The Atlantic barrier islands extend from Canada to Florida, then up Florida's Gulf Coast and all the way around to Mexico. Prior to development, many of these islands came and went at the whims of the tides and storms. Now that we've built homes and resorts on them, there is a vested interest to make them more permanent by using jetties to block the outflow of sand and beach replenishment to restore what's been lost. Let's take a look at the natural history of where you built that sand castle.

Grassy dune in New Jersey

Barrier islands, if left to nature, live and die by the tides. Ocean currents carry sand away from the islands. The sand either moves out to the sea floor, where it can be brought back to the island by currents, or it is carried to another part of the island or to a different island. Strong storms can accelerate the process, wiping islands off the map or opening up a new inlet to the back bay.

Hurricane Irene cut these inlets across Hatteras Island (NOAA) 

Barrier islands can move toward the mainland as wind blows sand over the dunes to the bay side. The marshes fill in with sand and build up new dunes, while ocean moves to where the dunes originally were and new marshes form in the bay on the edge of the old marshes.

Salt marsh at Assateague Island (NPS)

The islands are important because they are barriers protecting the mainland from such storms. A few weeks ago we looked at hurricanes on this blog. Barrier islands absorb the brunt of the storm surge that comes in ahead of the hurricane. Developed barrier islands still absorb the storm surge, but not as well as undeveloped islands from times past. Impermeable surfaces like roads and parking are terrible at absorbing water, while sand drains quickly. If the dunes have been removed from an island, the storm surge rushes right over top with nothing but buildings to slow it down.
Barrier islands are also important as habitat for critters other than summer vacationers. On an undeveloped island, different plants and animals that can tolerate different amounts of salt water and exposure to the air make their homes in different zones. Clams live beneath the sandy shore, while birds that prey on them scurry above. Grasses hold the dunes in place, and at the highest points of the island you can find trees and shrubs where songbirds and mammals live. Brackish marshes on the other side of the dunes host crabs and serve as a nursery where fish can eat and grow before venturing into the open sea. Wading shorebirds take advantage of this bounty. Beyond the marsh is the back bay and the mainland.

Ghost crab (NPS)

Sandpiper feeding frenzy

The US has more barrier islands than any other country in the world. Best known are New York's Fire Island, Texas's South Padre Island, the Outer Banks of North Carolina, and the Jersey Shore. If you spend a summer weekend at the beach, be sure to check out the wild side of things.
This week's information comes from Science News for Students.

Species of the Month

Wherever you live, fishing season is in full swing. This month we'll profile one of the most common game fishes, the rainbow trout. They can be found in lakes and streams almost everywhere around the world, though introduced to many of them.

Rainbow trout (State Department)

Scientific name: Oncorhynchus mykiss

Kingdom: Animalia (animals)

Class: Actinopterygii (ray-finned fishes)
Order: Salmoniformes 

Range: Pacific coast of North America from Alaska to Mexico

Habitat: Aquatic, some also have a marine phase

Lifespan: 6-8 years average, up to 11 years
Diet: Insects, insect larvae, crustaceans, small fish, algae
Predators: Lampreys, eagles, osprey, herons, mergansers, bears, mink, river otters, seals, sea lions, other fish, humans

Fish on! (NPS)

Conservation Status: No special protection for freshwater only fish; nine populations of steelhead are listed as threatened or endangered

Steelhead (NOAA Fisheries)

Other information: Rainbow trout get their name from a colorful iridescent streak along the sides of its body. State fish and game agencies around the country raise them to stock streams and lakes for fishing season. Stocked trout remain in freshwater; some native trout along the west coast are anadromous (have a saltwater phase) and return to their birthplace to spawn and die. The anadromous trout are called steelhead. Females lay eggs in a gravel nest called a redd. Fertilized eggs hatch after a few weeks, and the hatchling remains attached to the yolk sack as a food source before leaving the redd for the wider world. Young trout tend to stick to slower, shallow water. Young steelhead remain in the stream for up to three years before heading out to sea. Due to habitat degradation and loss, several western steelhead species are listed as threatened or endangered under the Endangered Species Act. Meanwhile, introduced trout are becoming a problem in some areas. They eat and/or outcompete native fishes such as cutthroat and brook trout. They threaten genetic integrity by hybridizing with native species. They also carry a parasite responsible for whirling disease, which causes deformities that make a fish easier prey.

Steelhead (NOAA Fisheries)

This week's information comes from University of Michigan's Animal Diversity Web and the US State Department, of all places.

Cave Life

This week is Cave Week, so to celebrate we're going spelunking to see what critters we can find. In addition to all sorts of whimsical formations, caves host a surprising amount of life. There are trogolobites, which live full time in caves; trogolophiles, which live in a cave but can also survive outside; and trogoloxenes, the part time cave denizens. You can encounter insects, fish, birds, mammals, plants, fungi, and others. Because there is very little natural light, many of these species are adapted to live in darkness; some don't even have eyes.

Whimsical cave formations

The first cave critter that comes to mind is a bat. Many bats roost in caves because they are cool and dark during the day, making it easier to sleep. Caves make a great place to hibernate over the winter. A constant temperature that is above freezing is an obvious plus, but it's cool enough to trigger the hibernation process. Other cave mammals include bears and jumping mice.

To the bat cave! (National Science Foundation)

Plants are a rare find in  caves because they need sunlight for photosynthesis. I saw ferns growing in a cave under a ceiling hole that opened to the surface. Much more common are fungi, which thrive in dark, damp conditions. Most important among them is Pseudogymnoascus destructans, which causes White Nose Syndrome in bats. It is devastating bat colonies across the US and Canada, and enjoys the cool temperatures while the bats hibernate.

White Nose Syndrome affecting these bats (NPS)

Cave fish are interesting little critters. Nearly all lack eyes and skin pigment. With no light to see by, there is no need to camouflage or stand out, so they are likely to be white or light colored. Unable to see their food, they find it by sensing movement in the water. What exactly do they eat? Since plants, the base of the food chain can't really live in a cave, anything in there either needs to go outside for good or eat whatever gets brought in. Cave fish eat detritus that washes in during rain events. Other critters get by on dung, the leaving of larger animals that way out.

Blind cave fish (NPS, Rick Olsen)

Cave Week runs through this weekend. Find a cave near you and check it out. Spelunk safely. Use the buddy system, carry at least three light sources, and make sure someone knows where you are going. Don't disturb any wildlife and make sure clothing and equipment are thoroughly cleaned before entering another cave. This helps prevent the spread of White Nose Syndrome.
This week's information comes from the National Park Service and National Geographic.