Community
Bringing Citizen Science To Lake Pupuke
GUE diver and aquatic eco-toxicologist Ebrahim Hussain applies some serious citizen science to get to the bottom of the trouble in Lake Pupuke, New Zealand. Project Baseline is alive and kicking, thank you very much!
by Ebrahim Hussain
I have always been passionate about aquatic ecosystems and how they work which inspired me to become an aquatic ecotoxicologist. I have always tried to document observations in an attempt to better understand environmental changes. The biggest challenge I have faced was getting my observations to organizations that are able to use them in a constructive manner. We all constantly see changes in our environments but are often unable to make a positive change.
Citizen science is a greatly underutilized resource by regulatory agencies. There are a myriad of citizen science groups that actively want to participate in the monitoring of their local ecosystems, but they lack the guidance or platform to do so. The Project Baseline Initiative provides an amazing platform for people to display their findings, and in combination with guidance from local authorities, the resulting projects can be an overwhelming success. This article will hopefully take you through my journey to improve a local lake that means a lot to me and the people who use it.
Lake Pupuke is a 186 ft/57m deep volcanic crater lake with a surface area of 110 hectares that drains a 105 hectare urban catchment in Auckland, New Zealand’s North Shore. The influence of this urban catchment on lake water quality is enhanced by the fact that the lake has no direct in and/or out flows and consequently has a high water retention time. Water enters the lake via a variety of diffuse sources (runoff, groundwater & precipitation) and exits through evaporation and intermittent drainage channels.
The lake is used for a variety of recreational purposes and is a venue for national and international events. The lake is also widely used by dive schools and boat clubs from across the region as a training facility.
A Lake Under Threat
I have been diving in Lake Pupuke since 2013, and I quickly came to realize that this lake was under threat. The water clarity had decreased, and according to the local dive schools, this deterioration had been noticed for many years prior. In the summer of 2014 a thick algal bloom developed which had not been recorded previously. The initial concern was the potential human health risk associated with algal blooms, but samples taken by the Auckland Council identified the bloom as Ceratium hirundinella which is a nontoxic species.
It was quite puzzling that even though Ceratium has always been present in the lake it had never formed large scale blooms until 2014. It was thought that this bloom was a once-off event until it occurred the following year and every summer since.
Ebrahim Hussain installing a dissolved oxygen & temperature sensor on the monitoring station. Photo by Andrew Davidson.
In an attempt to understand what had caused this change, I began looking at the Council’s long-term monitoring data, and to my surprise, I could not find anything that pointed to the exact cause of these recurring blooms.
I initially looked at temperature and nutrient loads which are the most common drivers for algal blooms and found that the lake had not been significantly warmer than previous years, and the trophic level index, while elevated, was within the same variance seen over the past ten years. However, there was no associated metadata to support any conclusions. It was clear to me that we could not fully understand what was happening in the lake through seasonal surface-based water quality sampling alone, and that regular subsurface observations were needed.
Enter Project Baseline
That is when I came across the Project Baseline Initiative, and it was the perfect platform for the type of work I wanted to conduct. The primary focus was to collaboratively work with volunteers, local communities, research organizations, and the Auckland Council to collect data that would complement the work already being done by the Council, as well as to specifically address the subsurface knowledge gaps. By doing this we are able to make use of both Council-funded and citizen science-driven data acquisition to support and inform a more holistic management strategy for Lake Pupuke.
We initially started collecting very basic data, such as visibility, temperature, and general meteorological information, but this quickly ramped up once we started noticing what was happening underwater.
We installed continuous temperature sensors, which log data every 15 minutes, at various depths to get a better understanding of the seasonal thermal stratification in the lake. Our data indicates that the lake usually stratifies from October until June, with an average winter temperature difference of 0.7°C between surface and bottom waters, and a summer difference of 10.2°C.
Stratification in lakes of this depth is a natural result of the surface water layers being heated by the sun. This heating causes the formation of a thermocline where the warmer water layer sits above the cooler, denser bottom water. This process separates the water column into three distinct layers, the epilimnion which is the warmest layer on the surface, the cooler metalimnion in the middle, and lastly the hypolimnion which is the coldest layer at the bottom of the lake. This separation of layers reduces the mixing of heat, oxygen and nutrients between the surface and bottom waters.
It is important to track these changes in stratification because it is directly related to the potential oxygen cycling and internal nutrient loading within the lake.
We installed continuous dissolved oxygen (DO) sensors within these distinct thermal layers to assess this oxygen cycling, and what we found was surprising. In winter the DO% on the surface ranges from 86% to 98% and gradually drops in even gradations down to about 40% at 55m. In summer the DO% ranges from 80 to 90% on the surface down to less than 3% at 55m. This is expected, but what took us by surprise was the presence of midwater anoxic layers, one near the surface between 7m-9m, and a second layer in the metalimnion between 12m-16m.
The Results
After seeing this, we began investigating other potential DO dead zones in the lake using multi-parameter water quality meters and have since identified additional areas. There was evidence of anoxia in the macrophyte beds that surround the lake, so we deployed additional sensors, and our finding confirmed our initial assumptions with summer DO% dropping to less than 3%.
This is critical information, as anoxic sediment conditions actively promote the remobilization of nutrients which further contribute to the eutrophication of the lake and drive algal bloom formation. These conditions can also cause the release of ammonium & hydrogen sulphide which are all toxic in high concentrations.
The next question we had was what was causing this anoxia. It is natural for a lake this deep to have anoxic bottom waters during summer, but we did not know what was causing this anoxia midwater and in the macrophyte beds. The dense macrophytes stop water from freely flowing into the shallows, and there is a lot of visible organic material that is decomposing on the bed, which all contributes to the anoxia.
The increased load of organic material, composed of dead macrophytes & phytoplankton, seemed to coincide with the appearance of the algal blooms. To prove this we installed light sensors that continuously measure the photosynthetically active radiation attenuation at various depths. The data shows that at on average there is almost no usable light past 4m after 13:00 and zero light penetration past 10m during the summer blooms. This lack of light caused the macrophytes to die, and coupled with the dead phytoplankton settling down, created an influx of decaying matter on the lake bed. We now regularly conduct macrophyte extent surveys to document seasonal die back and regrowth.
We knew where the additional organic material was coming from and what was causing the anoxia in both the macrophyte beds and the hypolimnion. The next question was how many nutrients are being released from these areas and what is causing the midwater anoxia. To answer this, we started a collaborative project with the Auckland Council and the Cawthron Institute.
The first step was to install sediment traps at various depths to understand how much organic material is produced midwater and how much settles down to the bed. The second step was to take a suite of sediment cores from the areas of concern we had previously identified to understand the amount of nutrient remobilization that occurs under various environmental conditions. The third and final step was to take targeted water quality and phytoplankton samples from the midwater anoxic layers to understand how/why they are formed.
The majority of the sampling required has been done except one more round of winter sediment traps. Once this has been completed, all the data will be analyzed and will fill a critical knowledge gap regarding internal nutrient cycling. This in turn will help guide the next steps for the wider project as well as inform potential mitigation measures.
Project Baseline has provided an amazing tool to facilitate the collaboration between citizen science and local government by formalizing community-driven data collection. The Project Baseline Lake Pupuke Initiative is a proven example of how citizen science can be used to satisfy critical knowledge gaps and directly feed into regulatory strategies with the common goal of creating a better, healthier environment.
Ebrahim Hussain is an Aquatic Scientist working at the Auckland Council. He began diving when he was 12 years old and has never looked back. Hussain studied aquatic ecotoxicology and zoology at university, and it was clear that he wanted to spend his life studying these subsurface ecosystems and the anthropogenic stressors that impact them. Hussain founded Project Baseline Lake Pupuke with the goal of contributing to preserving and enhancing this natural beauty as well as encouraging others to get involved in actively monitoring their natural surroundings.
Cave
The Aftermath Of Love: Don Shirley and Dave Shaw
Our young Italian poet-explorer Andrea Murdoch Alpini makes a pilgrimage to visit cave explorer Don Shirley at the legendary Bushmansgat cave in South Africa. In addition to guiding the author through the cave, Shirley and Alpini dive into history and the memories of the tragic loss in 2005 of Shirley’s dive buddy David Shaw, who died while trying to recover the body of a lost diver at 270 m/882 ft. The story features Alpini’s short documentary, “Komati Springs: The Aftermath of Love.”
Text by Andrea Murdock Alpini
🎶 Pre-dive clicklist: Where is My Mind by Pixies🎶
South Africa, Komati Springs.
On October 28, 2004, two cave divers and long-time friends, Don Shirley and David Shaw, planned a dive at Boesmansgat (also known in English as “Bushman’s Hole”) a deep, submerged freshwater cave (or sinkhole) in the Northern Cape province of South Africa. Dave dove to 280 meters, touched the bottom and started exploring. At that time, Shaw had recently broken four records at one time: depth on a rebreather, depth in a cave on a rebreather, depth at altitude on a rebreather, and depth running a line. While on the dive at Boesmansgat, he found a body that had been there for nearly ten years, 20-year-old diver Deon Dreyer.
After obtaining permission to retrieve the body from Dreyer’s parents, the two friends returned three months later. They enrolled eight support rebreather divers (all of whom were close to Don) and Gordon Hiles, a cameraman from Cape Town, who filmed the entire process—from the preparation on the surface to the operation at the bottom of the cave. The surface marshal was Verna van Schaik, who held the women’s world record for depth at the time. Little did they know that Dave would not come back from his 333rd dive, one that he himself recorded with an underwater camera.
Researchers have determined that while attempting the retrieval, Dave ran into physical difficulties with the lines from the body bag and the wires from the light head. The physical effort of trying to free himself led to his death for what is believed to be respiratory insufficiency (see video below). Don Shirley nearly died as well, and apparently was left with permanent damage that has impaired his balance.
Nearly 20 years later, our own Andrea Murdock Alpini visits Don and has this to say:
February 2023—I arrive at the mine owned by cave expert and pioneer of deep diving, Don Shirley. The place is fantastic—the wild nature, the warm water, and the dives are amazing. Every day I spend at least 230 minutes underwater, filming the mines and what is left of man’s influence in this beautiful and God-forgotten corner of Africa. Every day I have time to talk, plan dives, and prepare the blends together with Don Shirley.
The following is a part of the story that links Don Shirley to South Africa. Stories and places intertwine between Komati Springs, Boesmansgat (or “Bushman’s Hole”) and then the fatal dive with his friend Dave Shaw.
Monkeys arrive on time every 12 hours. They showed up last night at about 5:00. They came down from the trees in large groups. They start playing, throwing themselves from one branch to another, chasing each other. Mothers hug their little ones. Some of them play with oxygen cylinders, the smaller ones instead with methane gas tanks, the ones we use for cooking. We are surrounded by gas blenders of all kinds.
A herdsman’s hat rests on the workbench. Two hands with delicate, thin skin take adapters, cylinders, and whips.They open and close taps. Notebooks report all the consumption for each charge, strictly written in liters with the utmost precision. Impressions: An Amaranth t-shirt, an unmistakable logo, that of the IANTD. A pair of jeans and then some boots. He has a slight physique, he is lean and athletic with a beard that is white now, and a few days’ old.
While he works carefully, I do not disturb him, for I know well that when mixing, one is not to be interrupted, at least this is so for anyone who loves precision. Then, when he’s done, we have time to talk a little bit together.
We sit at his desk and then go to the board to plan the dive in the mine.
Don shows me the map of the first level. He explains some important facts to me, then his hands pull out a second sheet with the plan redesigned from memory of the second level at 24 m/70 ft deep. “This is the guitar level,” he says.
At first I don’t understand. He chuckles. I look at the shape he drew and, yes, that floor plan is a cross between a Fender Stratocaster and a Picasso guitar. Anyway, it’s a guitar, no doubt.
We begin planning the dive together. It’s exciting to hear him talk; he speaks in a soft, elegant tone, and it moves me. I look at his index finger moving. I listen to his words, but I also look at his eyes.
He gives me some advice but also tells me, “This mine is more similar to a cave. I have left it as it is. I want people to explore it and not follow any lines.”
Freedom of thought, plurality of choices. Acceptance of risk, inclusion of the other in what belongs to you. It’s clear that Don’s vision of diving is uncommon. Freedom is beautiful, but it is the most dangerous thing there is, if mishandled.
The next day, we have an appointment at 7 o’clock at the lake. Before diving this morning, we saw where the “Tunnel of Love” originates on the surface, a curious gallery which I came across underwater. There are two parts of the mine that survived the destruction of the mining facility after its closure. One of these is the tunnel where we are going, the other part is perched in the middle of the mountain.
Don explains that the tunnel is now frequented by the wild animals who go to drink there, so we follow their trail. The water has flooded everything up to just a few meters below the surface of the bush. Don cuts the underbrush that makes the path difficult. He wears his faithful herdsman’s hat and never takes it off. The ground begins to tilt slightly, a good sign that we are about to arrive. A series of stones suggest that here the path has been paved. “It was covered in wood,” Don explains.
The path that started from the building where the miners lived is now demolished. Following it, we arrive at what was called “The Tunnel of Love.”
The tunnel that was the mine’s main entry point. Narrow and difficult, the tunnel led to level one—now underwater at a depth of 18 m/60 ft.
We turn on the headlamps and enter. A small colony of bats flaps its wings upon our arrival. The water touches our boots. Some roots filter from the rock and stretch to the resurgence. The scenery is evocative.
Don kneels, peering at the water, and something. He looks at the water and something changes within him. Something has changed in our shared dialogue.
It’s as if Don takes on another language as he speaks. He always looks straight ahead. His vocabulary changes, and with it his tone of voice. We talk about politics, economics, the future of Komati Springs, the origin of the name of the place, the history of the mine, but we never mention two topics: diving and Dave Shaw.
Don’s a real caveman. I know that those who love caves are not ordinary people. We who do are a little bit mad to do what we do and love, but he’s different. He is comfortable here; he has found his dimension.
I remember asking him a question when we were inside the Tunnel of Love, breaking one of the long silences: “What thoughts are going through your mind?” He seemed to have reached a meditative state, a kind of catharsis. He replied, “I am just relaxing. This is a peaceful place. “
Around nine o’clock, we travel again to the lake, leaving the dry caves behind.
The first dive lasted 135 minutes, the second 95 minutes. Once the equipment is set up, I return to the cottage to dry everything and recharge the cylinders.
Don’s hands this time are again without gloves. Before we start mixing, we walk into his office.The walls are lined with articles he has published over the years.
He shows me the medals for valor he got when he was on duty in the British Army. When we return to a small corridor that acts as a barrier, my eyes fall on two photographs. “Is that Dave?” I ask. “That’s him. We were here in Komati,” Don tells me. “You see? This is his hat,” and he points to what is on his head.
The Consequences of Love
These are the consequences of love, I think. A friendship that transcends time, life, but also death.
It’s time to prepare the blends for tomorrow. As the oxygen pumps out, Don asks me, “Have you ever seen our Boesmasgat’s diving slates?” Obviously, I had never seen the decompression tables of that famous and tragic dive to 280 m/920 ft depth at 1,600 meters (nearly 5,000 feet) altitude.
“Hang on a sec.” Don picks up a small black box with a yellow label and brings it to me. He opens it. “These are the original dive charts. These are mine; these are Dave’s.” The box also contains the famous blackboard with the inscription, (“DAVE NOT COMING BACK”) from the documentary, as well as a pair of underwater gloves used in that dive, and then the heirloom of his CCR computer that broke due to excessive hydrostatic pressure.
He exits the room. He leaves me with those emotionally charged objects in my hands. I can’t see them any differently. They obviously have historical value; but, for me, the human sense prevails. I look at the decompression tables, touch the gloves, and think about the hands that wore them, that read the various whiteboards, and I imagine the scenes of that time.
I place everything back in the box. I hand it to Don as I would hand him a precious urn. In part, it is one. I find it hard to express myself in that moment. He understands why.
At this point I ask him, “What was the true meaning of that extreme dive that Dave wanted to do? Why did he do it?”
“He just wanted to explore the bottom of that cave,” Don said. “Wherever Dave went, he wanted to get to the bottom. That’s how we’ve always done it together. So that’s what we did here at the mine.”
Don then tells me a series of details and information about that place, about the geological stratification of the cave; he talks a little about the owner of the land where the famous sinkhole is located, and finally he talks about many other aspects of their failed dive. I promised to keep it to myself, and I will do so, forever.
Such is a connection that endures over time.
DIVE DEEPER
Wikipedia: Dave Shaw
YouTube: Diver Records Doom | Last Moments-Dave Shaw
Wikipedia: Dave Not Coming Back (2020) A critically acclaimed film that centers on diver Dave Shaw’s death while attempting to recover the body of Deon Dreyer from the submerged Boesmansgat cave in 2005.
Shock Ya: Don Shirley Fondly Remembers Scuba Diving with David Shaw in Dave Not Coming Back Exclusive Clip
Outside: Raising the Dead (2005) by Tim Zimmerman
Other stories by the prolific Andrea Alpini Murdock:
InDEPTH: Finessing the Grande Dame of the Abyss
InDEPTH: Hal Watts: Plan Your Dive
InDEPTH: I See A Darkness: A Descent Into Germany’s Felicitas MineInDEPTH: Stefano Carletti: The Man Who Immortalized The Wreck of the Andrea Doria
Andrea Murdock Alpini is a TDI and PSAI technical trimix and advanced wreck-overhead instructor based in Italy. He is fascinated by deep wrecks, historical research, decompression studies, caves, filming, and writing. He holds a Master’s degree in Architecture and an MBA in Economics for The Arts. Andrea is also the founder of PHY Diving Equipment. His life revolves around teaching open circuit scuba diving, conducting expeditions, developing gear, and writing essays about his philosophy of wreck and cave diving. He published his first book, Deep Blue: storie di relitti e luoghi insoliti (2018) and IMMERSIONI SELVAGGE, published in the Fall of 2022.
