DELTA STEWARDSHIP COUNCIL: Non-native species in the Delta, Contemplating the future of the DISB, and Regional San treatment plant upgrade

At the May meeting of the Delta Stewardship Council, Dr. Steve Brandt, Chair of the Delta Independent Science Board, provided a brief background on the Delta Independent Science Board, reported on the Board’s recently completed review on non-native species in the Delta, and discussed the Board’s approach going forward in light of the recent compensation issues.  Also, Dr. Laurel Larsen spotlighted a recent study looking at the effects of the Sacramento Regional Sanitation District plant upgrade on phytoplankton.

Background on the Delta Independent Science Board 

The Delta Independent Science Board (or DISB) is consists of 10 scientists selected through a nationwide search conducted by the Lead Scientist and chosen by the Delta Stewardship Council.  The DISB has been in existence for 11 years.  Recently, six members of the original Board had to step down due to term limitations, so there are six new board members as of September 2020.

The Delta Independent Science Board has a statutory responsibility defined in the Delta Reform Act to provide oversight of the scientific research, monitoring, and assessment programs that support adaptive management in the Delta through periodic reviews of the programs.  The DISB also provides independent advice on the Delta Plan and helps the Council appoint the Lead Scientist.

As stated in your charge to us as well, we are an independent body, and we think that independence helps us to provide stakeholders with the trust needed to evaluate the science and allow you all to use that science in your deliberations,” Dr. Brandt said.  “You also said that our recommendations, and I quote, ‘must reflect high scientific and technical standards, and the widest possible representation of knowledge, disciplines, and trends of thought.’  So we take that seriously in what we do.” 

The DISB performs its review function in two ways: Reviewing agency documents and conducting more extensive thematic program reviews.

The DISB provides scientific evaluations and reviews of agency documents, such as the Delta Science Plan, the Delta Plan amendments, the Bay Delta Conservation Plan, and various white papers issued by the Delta Science Program and the Council.   

The DISB also performs large-scale, in-depth thematic reviews in which the Board looks at the science that’s available worldwide, as well as the science being done in the Delta. The Board has finalized seven reviews on restoration, fish and flows, adaptive management, levees, the Delta as an evolving place, water quality, and the Interagency Ecological Program.

The general purpose of the reviews is to evaluate the state of the science, see what’s being done in the Delta, and look for gaps.  The DISB then provides recommendations to increase scientific credibility, improve the research clarity, advance the debate about Delta issues, and strengthen the connection between science and policy issues.

The Delta Independent Science Board does not make or recommend policy decisions,” said Dr. Brandt.  “Our goal is to be independent of the policy decisions and just provide the evaluation and overview of the science that is being done to support those decisions.”

The DISB is currently completing a review of water supply reliability and another on monitoring, which is the most extensive review so far.  The Board is also working with DPIIC to put together a science needs assessment based on ecosystem forecasting that is nearly completed.  And today, Dr. Brandt will give a brief overview of the recently completed review on non-native species in the dynamic Delta.

The process for these reviews is by the theme of what needs to be reviewed,” said Dr. Brandt.  “We do a lot of work with stakeholders. We have a lot of discussions with panels.  We then prepare a two-page prospectus that more or less says, ‘here’s what we’re going to do, here’s why we’re going to do it.’  And it’s important to get public comment on that.  We get public comments throughout our process. And our final requirement is to make this report available and report to the Council on this.”

Over the recent years, the Board has expanded its outreach after the review is complete through presentations at conferences, flyers, publications, and various stakeholder meetings.  The DISB works with stakeholders before, during, and after a review with frequent meetings within the Delta to get a real feel for the Delta issues and the stakeholders’ concerns and priorities.

DISB Review: Non-Native Species in the Delta

Dr. Brandt then turned to the recently completed review on non-native species in a dynamic Delta.  It was a topic chosen because non-native species are one of the most significant global threats to the integrity of ecosystems and one of five key drivers of ecosystem change.  The California Bay-Delta is considered one of the world’s most invaded estuaries. It’s also a key component in the Delta Reform Act, which states that a Delta plan should restore a healthy ecosystem by promoting self-sustaining, diverse populations of native and valued species by reducing the risk of take and harm from invasive species. It’s also a core strategy highlighted in the recent ecosystem amendment to the Delta Plan.

There are a lot of reasons for looking at invasive or non-native species and the science related to it,” he said.  “Perhaps the most important, though, is that non-native species threaten the achievement of the coequal goal that calls for protecting, restoring, and enhancing the Delta ecosystem.  In fact, non-native species even question our ability to define what the ecosystem actually is.”

The review aims to understand better the scientific need related to this complex issue in hopes that it will help agencies prevent and manage the threats and consequences of non-native species. There’s a tremendous amount of literature on this topic, and much is known about non-native species. So the DISB focused primarily on the Delta-wide needs spanning multiple agency responsibilities to identify a science-based prioritization framework to make decisions and allocate resources.

Each of the reviews is done differently, depending on the topic and nature of the review.  The non-native species review included an extensive literature review, not only the science being done in the Delta but worldwide.  The Board had two extensive panel discussions with experts who explored the status of science relative to non-native species.

This is typically the way we do business – day-long discussions and in-depth with experts in the area and experts outside of this Delta area, to really fully discuss the nature of what is needed on these topics,” he said.  “We’ve had a lot of deliberations and public comments, and we’ve participated in a lot of workshops, scientific sessions, and discussions with managers.”

Report findings

Dr. Brandt then highlighted some of the findings.  The first is that the science related to invasions and non-native species is extensive and spans over six decades: non-native species impact almost every ecosystem service and the very nature of ecosystem sustainability itself.  When a new non-native species enters the system, it can disrupt the entire ecosystem in unpredictable ways.

Given the degree of work that’s been done, the basic needs and technologies to better prevent, control, and ultimately manage individual non-native species are similar across ecosystems; routines have been worked out.  Science is needed at each point in the management decision process.

The Delta is a highly modified ecosystem. Many of the forces, locally and globally, that drive ecosystem and environmental changes in the Delta are ongoing, some even at an accelerated pace, particularly climate change. These changes affect the vulnerability of the Delta to new invaders.

What is unique in the Delta, relative to other large-scale ecosystems that are also facing invasion, are the particular institutional arrangements, scientific collaboration mechanisms, and funding structures to handle this issue,” he said.  “So our review is also looking at currently what exists, what entities are doing what, and how can we make recommendations to improve that within the context of the Delta.”

Report recommendations

The Board’s overall recommendation is to encourage a more ecosystem-level forward-looking, integrated approach to non-native species science in the Delta with specific consideration of climate change.

We highlight the importance of anticipation, or in other words, getting ahead of invasions for prevention and mitigation,” he said.  “We stress that science prioritization and stronger collaboration across disciplines is a critical need.”

Recommendation 1: Develop a comprehensive, spatially explicit food web model Delta-wide in scope and tied to environmental driving forces and conditions.

We have to figure out what’s going on; we really need to know who is eating who,” said Dr. Brandt.  “When a new species comes in, one of their primary influences is through the food web. And knowing the food web helps us improve our understanding of the non-natives currently in the system and what they are doing, but also predicting the potential impacts of new invaders. Without understanding that, it’s very hard to understand how a new invader might impact ecosystem services, particularly with respect to climate change.  Climate change influences the rates of many things, and understanding the food web is perhaps the most critical scientific need.”

Recommendation 2: Define and prioritize detailed short-term and long-term project-level science needs by conducting a series of focused workshops or syntheses.

There are many smaller level project needs short term and long term at the project level, at the technical level, at the monitoring level, at the taxonomic level.  We suggest that these topic level science priorities at the project level be prioritized based on a series of focus workshops or syntheses, many of which are already underway in the Delta.”

Recommendation 3: Identify and prioritize new species that pose the greatest immediate and long-term threats to the Delta and reevaluate this list regularly.

The chart on the lower right shows how an individual non-native species is managed once it arrives.  The first question is a threat assessment: Are these things really something we need to worry about? Are they likely to get here, and are they going to cause harm? If so, we try to prevent them from arriving. If we fail, we need to do a quick assessment and try and eradicate the initial population. If that fails, we go into a control strategy to minimize the damage. And if that fails, we adapt to their existence in the system. Each of those management decisions requires science and monitoring along the way.

We cannot deal with every single possible species that may ever enter the system,” said Dr. Brandt.  “We don’t have the resources to do that. So the recommendation is to identify and prioritize new species that pose the greatest immediate and long-term threats to the Delta and reevaluate this list regularly.  We need to have a Delta-specific list. This should be based on the probability that they’re going to get here and survive, and the expected ecosystem and economic impacts that they might have once they arrive.”

Recommendation 4: Go beyond individual species management and set ecosystem-level goals that recognize an ever-changing species pool and changing drivers.

We need to go beyond this individual approach and realize that the ecosystem is changing. The ecosystem is often defined in many respects by that species pool – what species are there and how many are in that pool.  That changes by drivers: climate change, resource use, pollution, and land use can all change that species pool.  The species pool is also changed by new species coming in and by some species leaving the system or subtraction.  That species pool drives food webs, drives impact on native species, ecosystem services, habitat structure, and even water flow and quality.”

That species pool is dynamic. It’s changing all the time.  When a new species enters the system, by definition, that species pool has changed, and by definition, the ecosystem has changed. When we go back to protecting, restoring, and enhancing the Delta ecosystem, one could say, what is the ecosystem if it’s not a combination of the species pool that is there? It’s changing, and how do we define ecosystem goals in this context of a dynamic change of drivers, as well as the composition of the species that are there. We also think that this has implications for ecosystem restoration activities as well.”

Recommendation 5: Evaluate threat assessments for non-native species in the context of a changing environment and multiple drivers, especially climate.

We also recognize that climate change, in particular, is going to be changing what is going on,” said Dr. Brandt.  “Species will expand their ranges. Warmer temperatures and different changes in precipitation and so forth will change the susceptibility of the Delta to different species of possible new species. They will also change the ecosystem impact, and ecosystem impact occurring now maybe differ under climate change scenario.

Recommendation 6: Develop a comprehensive multi-agency invasive species coordination and implementation plan with the assignment of responsibilities and authorities that span monitoring, rapid response, control, and science expertise.

There are a lot of different agencies working on invasive species or non-native species in a variety of different ways,” said Dr. Brandt.  “One of the recommendations we make is that to implement things; we need a comprehensive multi-agency invasive species coordination and implementation plan. This plan has to have a specific assignment of responsibilities and authorities from monitoring to scientific expertise. There is a Delta interagency invasive species coordination team, which has made a good start in terms of communication element, but really, some specific plan is needed, we believe.”

Recommendation 7: Develop a single ‘go-to’ science source of expertise and information with proper authorization and funding.

 “We recommend developing a single go-to science source of expertise, with information, proper authorities, authorization, and funding. We call it a non-native species task force and non-native species science center that can range from a wide variety of expertise, including those that have taxonomic expertise.


Our conclusion is fairly simple: that science can be used to better predict, detect and control or adapt to non-native species and inform management to set ecosystem-level priorities,” said Dr. Brandt.  “Again, our goal is to have science that has a proactive understanding, and monitoring is critical, and that anticipation of what might become is really important.”

We need to be prepared, he emphasized.  What if a ‘newtrina’ (a hypothetical creature) shows up in the Delta?  Who are you going to call?  How will you deal with it?  What impacts will it have?

We don’t know any of that,” said Dr. Brandt.  “And we should have the science prepared so first of all, to make sure that we don’t have a surprise because we have enough background information. But if a surprise like this arrives, then we have the system set up, the plan set up, and the science available so that we can minimize any damage that might cause.”

Stakeholder assessment of the Delta Independent Science Board

Recently, the Delta Science Program conducted a survey and assessment of the Delta Independent Science Board.  Dr. Brandt shared the preliminary results.

The survey gauged stakeholder perception of the Delta ISB.  There were 174 responses, largely with state agencies, but also many federal, local, NGOs, private organizations, water contractors, and academics.  The green striped bars are positive; blue is not positive.   The respondents overwhelmingly responded positively to questions about whether the Board plays a unique role, whether it does not promote specific political agendas, and whether the Board itself provides that independent scientific oversight that’s needed, as shown on the graph on the lower left.

Other questions related to the DISB’s reviews and whether they were relevant, rigorous, and trustworthy.  Again, respondents were overwhelmingly positive.

Contemplating the DISB’s approach moving forward amid compensation issues

The Board is currently finishing two reviews and working on the Science Needs Assessment.  The Board has been discussing the approach to conducting future reviews, especially in light of the recent issues regarding compensation for the DISB members.

Dr. Brandt explained that last July, there was a significant change in the structure of their appointments and their compensation levels; individual contracts were eliminated and compensation significantly reduced.  This has resulted in a reduction in their ability to meet the statutory requirements.

Normally, we would hold many full day and a half or two day discussions, where we would be out in the field, we talk to stakeholders, we would spend a full day discussing a particular issue and debating what the scientific merits are and so forth,” he said.  “Under the new appointment structure, I don’t see that ever happening again. We’re now faced with one two-hour per month meetings.  That makes it challenging to do our statutory duties.  Things very likely will take longer, and, and we’ll do fewer reviews.

The Board is looking at how they might restructure their approach, possibly narrowing topics. However, he acknowledged the challenge of narrower topics, given the fact that the Delta is highly interconnected and complex.

I think the results on the invasive species report should give us all a lot of food for thought about how complex the Delta is, how it’s going to be changing over time, and how challenging it will be to manage this ecosystem – not only as an ecosystem, but also as an ecosystem within a major hub for our water supply of California, and the people that live and recreate and do business in and around the Delta,” said Dr. Brandt.

Our ability to be functioning independent Science Board has been fundamentally crippled by the changes in appointment,” said Dr. Jay Lund, Past Chair of the DISB.  “I think it’s evident that that’s the case from the tremendous reduction in the amount of effort. Essentially, most of us who put in time on this are putting that time in mostly as volunteers. And to get the kind of serious professional look at the science in this very complex system requires much more than what can be done with the current system of appointments.”

Dr. Lund noted that there is currently a bill, SB 851, which has passed the Senate and is in the Assembly, but it needs serious work and engagement.  The current version of the bill is basically a single line that says that the members of the Delta Independent Science Board cannot be employees of the state and cannot be employed by any of the agencies.

The intent, as I understand it, is to eliminate that option and, therefore, force us to go back to having contracts as we had before, both to guarantee our independence and tend to allow a significant compensation for the efforts of the board members,” said Dr. Lund.  “The interpretation, as I understand it, of the Legislative Counsel is that the current $100 per day per diem compensation for the board members is not necessary and that contracts are an allowed form of compensation. But I think there’s some uncertainty about that, certainly in many parts or some parts at least. And so hopefully, there will be some discussions between different levels of the administration and legislature to work this out, so hopefully, we come to look at this as a bureaucratic snafu in the rearview mirror.”

Obviously, without an ISB, we’re paddling upstream without a paddle,” said Councilmember Damrell.  “It’s very difficult. Our task is impossible. So I think we need the Delta Independent Science Board, and I hope that this legislation will resolve the problem.”

During the discussion period, Councilmember Virginia Madueño asked about new species that significantly impact ecosystems. Are you seeing some of these new species?  What are they, and what are the most devastating impacts that you see?

Certainly in terms of the Delta, there’s a lot of history in terms of how species have come in, one way or another, and changed the ecosystem,” said Dr. Brandt.  “The overbite clam has affected a lot of the lower food web and how things permeate up through there, the current issue with the emergent vegetation blocking Delta transportation, and the nutria is certainly invading. There are tremendously coordinated efforts with DPIIC and multiple agencies; there is a task force trying to eradicate it wherever it’s seen in the Delta.  That could have direct ties to the levees and as well as other critters. “

In terms of what’s coming down the pipe, the state of California has a list of several species; I think the Department of Fish and Wildlife has their list as well,” continued Dr. Brandt.  “That would be a place to start with that list, which is California-wide, and seeing what those critters might do if they get into the Delta. But the Delta may be more vulnerable to certain species and less so to others. The zebra mussel and quagga mussels are certainly something that is a huge threat throughout California; they’ve completely altered what’s going on in the Great Lakes, which is a massive system. And when they get into systems, the freshwater and low salinity systems around anywhere else, they can have a major impact. So that’s one I think that many people would highlight as one of the top ones to look at, but there’s a lot of them.”

Dr. Lund noted that we often see some of these regime changes, particularly in the Delta, come around during droughts. “Overbite clams came in during the 1988-92 drought. We also tend to see an expansion of the areas of aquatic weeds during times of drought. So we might be seeing a lot more activity in terms of expansion of some of the areas of invasive species that are already here or new ones that come in. Droughts are an opportunity for them.”

Members of the public speak in support of the Delta Independent Science Board

During the public comment period, a handful of people spoke in support of the Delta Independent Science Board.

A letter from David Fries with the San Joaquin Audubon Society read into the record stated:

“ … It troubles us that the Council does not appear to be doing anything to rectify this problem. ISB members have been compensated fairly for more than a decade, and surely there’s a way to continue with major compensation. Apparently the Council ordered the Department of General Services to send the Delta ISP contracts back unapproved and did not tell anyone that they made the request.  In addition, the Council has refused all requests from the ISB for staff positions to aid in their review tasks.

One is lead to suspect that the Council is trying to disband or discredit the ISB as a means of considering only the size that it chooses. Does the Council really want to use the best available science in making its decisions? Is the Council more interested in pleasing the Department of Water Resources in the Metropolitan Water District or making fair and independent decisions on projects in the Delta? … “

Deirdre Des Jardins with California Water Research said they were troubled to learn that the DISB contracts had been requested to be returned.  “We haven’t been able to get a straight answer about why they were returned and what was the legal basis. I did have a conversation with the Executive Director in which she said that referred to constitutional considerations.   She said that I could have a call with the Delta Stewardship Council’s counsel, but I don’t think this is sufficient. I think there needs to be a written legal opinion. And the Council needs to review it. You also cannot delegate to your executive director the authority to reduce the funding of the Delta Independent Science Board below what’s needed to do their duty. So we’re very concerned that this decision seemed to have been made in secrecy. It was never brought for consideration before the full Council.

We request that you put this reconsideration of this item on the agenda. For the next meeting, you request that the Delta Stewardship Council executive director provide the legal basis that she made the decision to rescind the contracts and what that legal basis was because frankly, I have heard from a huge number of people that the legal basis for rescinding those contracts with the Department of General Services didn’t approve it because of AB 5 and that turned out not to be borne out. By the record, nobody is talking about AB 5 now.”

Ms. Des Jardins noted that it’s also a federal issue because the Cal Fed Record of Decision commits to an Independent Science Board that provides oversight and peer review of the overall program.  “If this isn’t resolved, the federal agencies are going to have to do something because their federal authorizing statute is still on the books. And it requires an Independent Science Board and independent peer review. So this isn’t a minor board. It’s not just a California state issue. It’s part of a 30-year legal commitment. And you absolutely cannot delegate this to the executive director.”

Osha Meserve, representing the Local Agencies of the North Delta and others, agreed that it’s essential to promptly resolve the issue with the DISB.  “In 2021, there may have been budgetary reasons that DSC executive staff was concerned about being able to meet the other obligations of this Council, but there’s no excuse for 21-22 in particular.  … We in the Delta, and I think everyone really benefits from Delta Independent Science Board because it’s a different voice that’s independent.”

Executive Officer Jessica Pearson weighed in after the public comment period, saying, “I think we’re all concerned about the capacity limitations on the Independent Science Board. And, unfortunately, the Council just does not have legal discretion to employ them as contractors going forward. So I am glad that there’s interest by the legislature to resolve the problem. I do believe that if there was a salary that was established by the legislature for the Independent Science Board, that that would be one way to address the problem going forward. And so we are available to answer questions from legislative staff on that issue. We’ve already been contacted to provide technical guidance. And so we’re very hopeful that there can be a resolution.

I just want to clarify that the council’s budget has not been reduced related to independent Science Board compensation,” Ms. Pearson continued.  “In fact, we’ve been working with the independent Science Board to provide at least what may be interim relief and support in the form of staff and postdoctoral scholars. We will be using funding typically set aside for the Delta independent Science Board to support that. So I do want to clarify that our budget has not been reduced. And if legislation were in place that set a statutory salary for the Independent Science Board that was in line with what they’ve historically been paid, we would have that funding available.

DELTA LEAD SCIENTIST REPORT: Article spotlight: Response Of Lower Sacramento River Phytoplankton to High-Ammonium Wastewater Effluent

Also at the May Council meeting, during the Delta Lead Scientist report, Dr. Laurel Larsen highlighted a recent article regarding the upgrade to the Sacramento Regional Wastewater Treatment Plant.

The Sacramento Regional Sanitation District (or Regional San) completed the upgrade to its wastewater treatment plant at the end of April, so the upgrade is online now and operating at full capacity.  

Regional San is the largest wastewater treatment plant in the Delta and the largest point source of nitrogen, one of the main macronutrients that support plant growth and primary production within the Delta. The NPDES permit issued to Regional San required upgrading its nitrogen removal capabilities to modern standards by building in tertiary treatment.

This new level of treatment reduces the total amount of dissolved inorganic nitrogen in its waters and changes the form of that nitrogen.  Formerly the discharge was highest in ammonium; with the new level of treatment, discharges are relatively low in ammonium but higher in nitrate.  The big question is, how will this change impact the Delta ecosystem?  Dr. Larsen noted that the question is one of the actions on the current Science Action Agenda.

It’s also a question with a long political history that traces back to pelagic organism decline or pod, which is the precipitous decline of most of the native fish species within the Delta that dates back to the 80s but was quite steep in the early 2000s,” said Dr. Larsen.  “Aligned with this decline was a crash at lower levels of the food web – the phytoplankton and zooplankton that ultimately supply energy to fish.”

One theory that has some support in field and laboratory observations is that elevated ammonium suppresses the ability of phytoplankton to take up nitrate, thereby resulting in lower abundances and shifts in species compositions that are unfavorable for the food web. However, Dr. Larsen noted there are also conflicting results from studies both inside and outside the Delta.

Now at the policy level, extrapolation of this theory is that dischargers of high ammonium into the Delta should pay for efforts to reverse POD through, for example, upgrading the wastewater treatment plant,” Dr. Larsen said.  “Before the NPDES permit was issued, however, Regional San claimed that altered flows were at the root of POD, and therefore that the water user users should be the entities financially responsible for reversing POD.

So the question of ecological impacts of altered nitrogen forms and amounts to the Delta is one with high stakes. The Delta Science Program has invested substantially in addressing this question through its funding of Operation Baseline, which ensured that appropriate monitoring was in place before the wastewater treatment plant upgrade came through in order to be able to document changes that could be causally attributed to the upgrade.”

Multiple research groups are tackling this topic from different angles.  One of those is the paper, Response Of Lower Sacramento River Phytoplankton to High-Ammonium Wastewater Effluent, is from Stanford University, authored by Strong et al.  This study was a laboratory study to observe how much and what kind of phytoplankton would grow in water that was sampled above and below the wastewater treatment plant.

In addition to incubations of the raw waters sampled from these locations, the researchers also amended additional samples with nitrate, other samples within ammonium, and the fourth set of samples with effluent from the wastewater treatment plant. Some samples were incubated under high light conditions and others under low light conditions.

What they found, in brief, was that the form of nitrogen had no impact on the amount or species composition of phytoplankton that grew in the samples,” said Dr. Larsen.  “What did influence the amount of phytoplankton was light level, which they were very sensitive to. Now that the wastewater treatment plant upgrade has come online, we will have the opportunity to robustly observe whether these laboratory results scale to the spatial footprint affected by the upgrade and to the long term.”

Another important question of interest not addressed in the article is the impact of changes in nitrogen concentrations on harmful algal blooms. 

It will be because of the Delta Science Program-funded Operation Baseline that these impacts will be possible to document, so stay tuned for some very interesting science that is due to come out over the next few years in association with this treatment plant upgrade,” concluded Dr. Larsen.

More information in Dr. Laurel Larsen’s written report:


Science Actions Workshop, July 13-14

Registration is now open for the upcoming Science Actions Workshop on July 13 and 14.  In the workshop, participants will work collaboratively to develop the near-term priority science auctions for the Delta. She reminded that these are the actions that drive funding of Delta science research.  In the workshop, the actions will be identified based on the collaboratively developed top 65 management questions that came out earlier this year, as well as on a summary of progress made on the 2017 to 2021 science action agenda.   Click here to register.


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