UH researchers test more sophisticated fish tracking.

You can radio tag a bird or a mammal to track their movements with GPS, but the technology doesn’t work so well under water.

Researchers have overcome this with satellite tags that report locations when whales or seals or turtles come to the surface. And there are tags that automatically release and float to the surface, where they can report their positions.

(Image: Map of fish tracking stations at Palmyra Atoll. Credit: UH Mānoa.)

But tracking a fish that stays down in the water can be a problem, so researchers have adopted sound waves as their tracking systems.

One solution has been acoustic monitoring, since sound travels well in the water. It works this way: you set up an array of precisely located listening devices on the reef. Then you attach small noisemakers to fish, and the sounds collected on the listening devices give you a sense of when fish are present and which microphone they’re closest to.

New research is fine-tuning the information.

“Previous methods were not formulated with the fish, ocean and acoustics in mind. They therefore do not exploit all available information, such as the biology of the fish limiting its range of possible movement.” Martin W. Pedersen, a UH Mānoa postdoctoral fellow.

Pedersen and Kevin C. Weng, manager of the Pelagic Fisheries Research Program at the University of Hawai‘i at Mānoa, published their new fish tracking model in the scientific journal Methods in Ecology and Evolution.

Pedersen and Weng’s new state-space model for estimating individual fish movement is two-part—one part that models the fish behavior, and one that models the detection of that behavior.

The system uses data on fish behavior, along with information on where fish are detected and where they are not detected to help pin down their precise locations.

“Knowing where the fish is not located actually tells you a lot about where it is located, and with our new method, we are able to utilize that information and achieve a better accuracy,” Pedersen said.

Their tracking model was tested in remote Palmyra Atoll, far to the south of Hawai`i, where 51 underwater observation stations were established. They were able to create maps that helped show where the fish were and how they moved.

“It helps us to better understand how they feed, breed and rest,” Weng said.  “Ultimately, more accurate movement information will help us to conserve these species.”

© Jan TenBruggencate 2013

Citation:  Pedersen, M. W., Weng, K. C. (2013), Estimating individual animal movement from observation networks. Methods in Ecology and Evolution. doi: 10.1111/2041-210X.12086

Coastal erosion in Hawai`i? It's sea level rise, silly.

Many Hawai`i beaches are eroding and it should be no surprise that the primary culprit is sea level rise.

Hawai`i researchers recently published a paper in the journal Global and Planetary Change that concluded that the main cause of coastal erosion in the Islands is rising ocean levels.

(Image: Maui beaches are eroding at an average of half a foot a year. Shown here is a coastal building on Maui, threatened by chronic coastal erosion. Credit: Zoe Norcross-Nuu.)

There are certainly other factors, like currents and the relative rise and subsidence of the islands themselves, but sea level’s the big one.

It means, in part, that people assuming those disappeared beaches will return cyclically to their previous size will wait in vain, and that the state’s decision-makers need to plan for continued coastal erosion.

“Shorelines find an equilibrium position that is a balance between sediment availability and rising ocean levels. On an individual beach with adequate sediment availability, beach processes may not reflect the impact of SLR. With this research, we confirm the importance of SLR as a primary driver of shoreline change on a regional to island-wide basis,” said Brad Romine, a coastal geologist with the University of Hawai`i Sea Grant College Program.

What he’s saying there is that if a beach still has a large natural dune system behind it—like, for instance, Polihale on Kaua`i—the sand will replenish the retreating shoreline and you’ll still have a beach. But of course, most of the state’s dune systems are long gone.

Sea level has been going up at nearly a tenth of an inch a year for most of the 1900s, but the level has increased recently to slightly more than a tenth of an inch a year—from 2 millimeters to 3 millimeters. That works out to sea level rise of three-quarters of an inch per decade accelerating to more than an inch.

Doesn’t seem like much, but at the current rate, a kid born today will see sea levels more than half a foot higher by retirement age. Imagine an additional seven or so inches on top of today’s highest tides, and the picture looks ominous for coastal roads, beach parks, coastal resorts, and sandy beach oceanfront homes.

That’s because each inch in sea level rise translates to several inches of coastal retreat. Maui beaches, of which 78 percent are eroding, have lost on average half a foot a year. Most O`ahu beaches are also eroding, but at a far lower rate, about an inch a year.

Some coastlines clearly get hurt more than others, and calculating the different coastal responses has been a major piece of Charles “Chip” Fletcher’s work.

“Improved understanding of the influence of SLR on historical shoreline trends will aid in forecasting beach changes with increasing SLR,” said Fletcher, Associate Dean and Professor of Geology and Geophysics at the University of Hawai`i School of Ocean and Earth Science and Technology.

Citation: B M Romine, C H Fletcher, M M Barbee, T R Anderson, L N Frazer (2013) Are beach erosion rates and sea-level rise related in Hawaiʻi? Global and Planetary Change, doi: 10.1016/j.gloplacha.2013.06.009

A press release on the project adds: “The research described in this paper was carried out by the University of Hawaiʻi Coastal Geology Group with the support of the State of Hawaiʻi; Counties of Kauaʻi, Oʻahu and Maui; U.S. Geological Survey; U.S. Army Corps of Engineers; NOAA; Hawaiʻi CZM; Hawaiʻi Sea Grant; and the Harold K.L. Castle Foundation.  This paper is funded in part by a grant/cooperative agreement from the National Oceanic and Atmospheric Administration, Project A/AS-1, which is sponsored by the University of Hawaiʻi Sea Grant College Program, SOEST.”

© Jan TenBruggencate 2013

Deep ocean canyons around Hawai`i are hot spots for species diversity

Often science simply confirms what you’d suspect. Example: Life is more interesting in a complicated landscape than a simple one.

(Image: Some of the canyons off Kane`ohe Bay. Credit: UH Mānoa.)

Case in point: You get more life and more kinds of life in the wrinkled landscape of Hawaiian undersea canyons than on the broad flats. 

University of Hawai`i marine researchers determined that biodiversity is significantly higher in the submarine canyons around Hawai`i than on the flats, largely because the canyons provide so many more types of habitat, but also because they concentrate nutrients.

The researchers reported in the journal Deep Sea Research Part II after 34 dives with the submersibles Pisces IV and V up and down the archipelago, from the main Hawaiian Islands to the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands. 

Their dives took them to study points at multiple depths, the deepest of them near a mile down. The principal researcher was UH oceanography professor Craig Smith.

In the canyons, they found both complexity of habit an increased biodiversity. 

 “Submarine canyons encompass myriad habitat types. This heterogeneity at the landscape-scale helps to enhance local biodiversity in canyon seafloor sediments,” said lead author Fabio C. De Leo, a doctoral graduate from UH Mānoa’s department of oceanography. Species diversity is considerably higher in canyons, he said.

In canyons, many things are happening. There are diverse physical habitats. Ocean currents are channeled. Sinking particles are captured. Too, a lot of the organic material washed off the islands ends up settling in canyons, where they decompose and add nutrients to a portion of the ocean normally limited in food availability. 

“When there’s more food, there’s more life,” De Leo said.

Says the University press release: “This series of dives was conducted on the Pisces IV and Pisces V manned submersibles operated by the Hawai‘i Undersea Research Laboratory (HURL).  The research was conducted in partnership with Hawai‘i Pacific University and the New Zealand National Institute of Water and Atmospheric Research.”

The paper’s abstract is here.

Here is the University of Hawai`i press release.

Here is the citation: Fabio C. De Leo, E.W. Vetter, C. R. Smith, A. R. Ashley, and M. McGranaghan.  Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands.  Deep Sea Research Part II: Topical Studies in Oceanography.  11 July 2013.

© Jan TenBruggencate 2013

Hawaii Energy Storage 9: A wrapup message: Follow the money

At the end of this series on energy storage, perhaps the best message is an old one in investigations.

Follow the money.

There is no end of storage technologies: regular chemical batteries, flow batteries, pumped storage, flywheels, heat storage and even phase change materials.

Which one will change the face of the energy landscape? That’s not yet clear.

And one reason is cost. Most of these technologies are still very expensive. 

(Here is a good place to insert a notice of conflict. I am an elected member of an electric cooperative board of directors. If lots of people go off-grid, it certainly impacts the finances of the co-op, but as a community co-op it’s also our imperative to serve the members, so if that’s the better alternative for them…)

I talked a while back with the son of an old Wisconsin farmer, who remembers his dad turning down a battery-based electrical system for the farm. At the time, there was no electricity at the farm. Kerosene lamps illuminated the place, and humans or animals did the work, not electric motors.

He turned down the battery system, in part because it was far more expensive than the anticipated power line that an electric cooperative would soon provide him.

“I’ll wait for the wire,” he said.

It costs a utility in Hawai`i $.30 to $.45 per kilowatt hour to deliver power to your house, as it does in other areas dependent on oil-fired power. It's a lot of money. Running your own power system might seem like a slam dunk.

But follow the money.

You may spend $.20 to $.25 per kilowatt-hour or so to make photovoltaic power at home (less with the tax credits included, but they may not be around a lot longer). It can cost another $.25 to $.75 per kilowatt-hour to store that energy for nighttime use—the numbers are all over the place depending on technology and system size and financing. (If anyone wants to nitpick these numbers, I’d be pleased to hear from you.)

If those numbers are good approximations, then without even talking about maintenance, equipment replacement, damage repair and so forth, the cost of your power is at a minimum equal to utility power, and at a maximum much, much higher. 

And and if you’re your own power supplier, you have the added benefit, when the lights go out, of personally responding rather than waiting for a trained lineman.

This is not to say going off-grid can’t work. It has always made sense in some limited applications—like a remote location where up-front infrastructure costs are prohibitive or a utility line isn’t available at all. It is not an accident that most home power magazines describe remote homes, far from existing grids. 

And it’s not to say that going off-grid might not make economic sense soon. When the price to make the power drops to a dime and it costs another dime to store it, that’s when the big crossover comes.

We’re not there yet. But we may be there within a very few years.

For utilities, which benefit from economies of scale, certain storage applications already make sense, but even for them, those applications generally require special situations.

© Jan TenBruggencate 2013

Hawaii Energy Storage 8: The fascinating world of phase change materials

They’re not batteries, they’re not thermal storage systems, but they still store energy.

You haven't heard much about phase change materials. You will.  Phase change materials are a range of compounds that have a huge energy signature when they change forms, or change phase, from liquid to solid or solid to liquid.

A common example is ice in a cooler. As long as ice is melting, it is absorbing heat from the beer and the outside of the cooler, and it keeps the temperature of everything around freezing. The temperature stays stable as long as the ice is changing phase and turning into water. Once the ice is gone and the melting process stops, the stuff in the cooler warms up.

You can develop materials that change phase at almost any temperature, and they work both ways--they can keep things cold, or alternatively, can keep things hot.

Japanese researchers at a recent energy storage conference said they are studying phase change materials to keep bentos hot. In this application, the materials changes from liquid to solid at the assigned temperature. As the food starts to cool, the phase change starts, the liquid changes to solid, and the process throws off heat. As a result, your bento stays at the assigned temperature and can't get cold.

You have heard of lithium ion batteries in laptops and Boeing jets that heat and even explode. You’ve felt your cell phone battery heat up. One researcher said a phase change material blanket could automatically a begin liquefying when a battery heats up, thus keeping it cool and preventing the explosion.

Researchers said you can dramatically increase the capacity of a home water heater by inserting rods with phase change materials inside. The phase change material stores a great deal of energy, and releases it as it changes phase. In this application, as the water temperature drops when you take a shower, the phase change material—presumably inside pipes in the water heater--begins solidifying, releasing heat into the water, without having to turn on the electric coils.

This means you could charge up a water heater when power is plentiful and cheap, and it could produce far more hot water for longer than standard water heaters of the same size.

I talked to a man whose company uses phase change materials to keep medical supplies cold for a week while they are being delivered to the military or third world countries.

A New Zealand researcher is mixing phase change compounds into drywall, keeping a house from getting too warm in summer or too cold in winter--without having to use electricity. It basically makes half inch drywall act like a thick concrete wall.

A German researcher talked about designing a modern supermarket to reduce lighting loads and improve cooling loads. They build icemakers into their big coolers to buffer their temperatures, and so they can turn off the power during times of high-cost power and still keep food cold. On stormy nights, when German windfarms produce more power than there is load, the price of electricity to supermarkets goes negative; they are paid to take power—they make ice with it.

When power rates go up, they can use the phase-change characteristics of the ice to keep the food cold without buying expensive electricity.

Next: Wrapping up energy storage

© Jan TenBruggencate 2013