Discovering Zooplankton in Crater Lake

An international volunteer records scientific data while sitting in a small boat at Crater Lake National Park.
Asuncion jots down scientific notes.

NPS Image.

My stay as an international volunteer at Crater Lake National Park (July 14, 2017 - August 13, 2017)


Being the Chief of the Biodiversity and Environmental Quality in the Environmental Department of the Council of Donostia/San Sebastian (Spain), one of the main goals I have is the management of the local natural areas. For that reason, my main concerns are the conservation and improvement of the Artikutza Natural Park (with a lake inside), the control of invasive species and the protection and restauration of the little streams.

I was really interested in learning about similar works in other countries, and staying in the Crater Lake National Park (Oregon) seemed to be a great opportunity to share and compare how to work with similar subjects, even if they are some differences due to the geological and geographical conditions.


The main objectives I had for my stay in the Park were:
- to understand the history, mission and role of the NPS and the Crater Lake NP s role in preserving and protecting aquatic resources
- to develop an in-depth knowledge about aquatic resources within the park
- to attend native cultural events and participate in local festivals
- to give a program to park staff about the parks in her country
- to learn about different ways of sampling and studying water chemistry, lake thermal structure, fisheries, zooplankton, and nearshore benthic vertebrates and invertebrates
- to learn operation of Niskin sample bottles, clean water collection techniques, measuring pH,
conductivity, alkalinity, operation of Seabird CTD, setting and retrieving gill nets, measuring fish length and weight, collection of zooplankton with vertical nets, of benthic insect samples and time constrained snorkel surveys for anphibians.


In order to achieve all the objectives, I have been working mainly with the Lake team, but also with other staff: Streams and Invasive Species teams.
I have also made some oral presentations about my work in Donostia/San Sebastian:
- Judy 17th, in the weekly meeting of the aquatic team,
- July 25th , in a general meeting with the superintendent and the heads of the different sections in the Park management,
- August 9th, in a “Casual Conversation” for Scientists Visitors like me and temporary staff working in the Park. In these cases, I have explained the 3 main lines I work with, showing that sometimes, our work is quite similar.

I have also had the chance of taking part in some local festivals or parties, like the “taco’s tuesday” with temporary staff, in a concert in a campground in the Park, in a Hawaiian festival and in a Country music festival in a village near the Park. In my free time, I have hiked some trials inside the Park: Gardfield Peak, Discovery Point, Castel Crest, Lady of the Wood, Godfrey Glen and Pinnacles.


During my program, I was working with the aquatic team, sampling in the Lake. Every year, in July (depending on the weather) they are taking different samples of water, to measure different parameters: oxygen, nutrients, chlorophyll, zooplankton, phytoplankton, conductivity...

The previous day, we have been preparing all the tools and bottles needed. I have learnt which kind of bottles they use to each parameter, in some cases preparing them with specific systems to disinfect them. Some of the samples have been analyzed in the Park’s laboratory, but some other have been sent to other laboratories.

These data collection are very important to evaluate the evolution and behavior of this lake, but also to compare it with other waters and then analyze in some cases the effect of Global Warming.

- NUTRIENTS: we have taken some samples in different springs, to measure amount other parameters: pH, alkalinity, nitrate, total Phosphorus, sulfate, orthophosphate...

- ZOOPLANCTON: due to the relative small numbers of inhabitants in the Lake, researches used a modified zooplankton net to be able to sample large areas of water and count the highly dispersed populations. This net concentrates the organisms in a little bottle at the bottom, in which the color changes according to the concentration of them. The samples were taken in different depths.

- CHLOROPHYLA: we have taken samples in different depths, putting each water in 2 kinds of bottles: a transparent one and a dark one. Then, a little amount of radioactive C14 has been added to each bottle, which is supposed to be absorbed be the organisms in the water. Having a dark bottle (without light inside, so without chlorophyll activity) and a transparent one, in which light actives photosynthesis, we can measure the different amount of absorbed C14, and as a result we know the chlorophyll level in each depth in the Lake.

- SEABIRD CTD: it is a specific transmissometer which provides information on water clarity at any depth. It is a more sophisticated device than a Secchi disk, since it passes a beam of light between two points to determinate the amount of particles in the water and thus measures the water clarity. A CTD controls the transmissometer and records the water clarity data it collects while also analyzing water conductivity, temperature, depth and other chemistry parameters below the Lake surface. One of the days, we have transferred all the data collected in 18 different depths during a year to the central computer. The Aquatic team has been using this kind of CTD since 1988, having one of the best
data collection in lake water in the world.

- FISH: we have been placing some gill nets and retrieving them the next day, to monitor the Lake’s fishes populations. More than a century ago, newts were the top of the trophic chain in the Lake, but Kokanee salmons and Rainbow trouts were introduced between 1888 and 1941 for recreational uses. This introduction has been successful and it seems to be the greatest human impact on the Crater Lake. Kokanee exhibit a boom and bust cycle in abundance over about 10 years, and when they are abundant, certain zooplankton becomes scarce due to predation.

In order to monitor these fishes populations,, they are putting overnight gill nets since 1986.
After collecting the fishes trapped in the net, we have recorded the amount, specie, sex, weight, length and maturity of each fish, as well as looking the inside of their stomachs to have more information about their diet.


To sum up, the experience has been really interesting and rewarding for me, both personally and professionally , and I would like to thank to the National Park Service for giving me this opportunity, to all the staff in the Crater Lake National Park for their patience and help, and specially to Mark Buktenika, who has been very generous and helpful for me.

Last updated: January 10, 2018