Environmental Drivers & Biological Sources of Inter-annual Variation in Net Primary Production by Giant Kelp Dan Reed Collaborators: Mike Anghera, Katie Arkema, Mark Brzezinski, Bryn Evans, Shannon Harrer, Brent Mardian, Bob Miller, Clint Nelson, Andy Rassweiler, Dick Zimmerman

Long Term Ecological Research (LTER) terrestrial / marine tropical / temperate / polar forests, deserts, grassland, alpine, tundra, agricultural lands, dry valleys, estuaries, coral reefs, kelp forests, pelagic ocean Network of 26 sites representing diverse ecosystems

Outline 1.Assess relative importance of different environmental drivers and biological characteristics of giant kelp in accounting for year-to-year variation in rates of net primary production 2.Describe a pathway by which natural ecosystems feedback to influence the environmental drivers that control them

The portion of gross primary production from photosynthesis that remains after plant respiration Represents mass of plant matter produced per unit area of the earth’s surface per unit time Net Primary Production (NPP)

DISTURBANCE FOLIAR STANDING CROP GROWTH NET PRIMARY PRODUCTION /- RESOURCE SUPPLY RECRUITMENT - NPP is the product of the density of actively growing plant mass and its rate of increase due to recruitment and growth + Biological sources of variation in NPP Environmental drivers of NPP

Giant kelp forests Macrocystis pyrifera Distribution of Macrocystis Promising system for investigating the relative importance of vegetation dynamics, recruitment, and growth in contributing to interannual variation in NPP

NPP by giant kelp is high and variable * * from Knapp and Smith 2001 * from Santa Barbara Coastal LTER Mean Annual NPP Interannual variation * * * * * * * * * * * *

Multiple processes interact to create a variable nutrient supply minhoursdaysmonthsyearsdecades millennia Internal waves Terrestrial runoff Wind-driven upwelling El Niño Southern Oscillation Decadal climate oscillations Global climate change local regional global

Occupancy of giant kelp on reefs in southern California Reed et al Pacific Decadal Oscillation warmPDO cool El Niño N = 69 reefs Frequent disturbance and rapid recovery

Question: What proportion of inter-annual variation in Macrocystis NPP is explained by inter-annual variation in : 1) Foliar standing crop at the start of the growing season (hereafter initial FSC)? 2) Recruitment of new plants during the year? 3) Annual growth rate?

Measuring Net Primary Production in giant kelp We estimate NPP as the product of growth rate and foliar standing crop integrated over the sampling interval g specific growth rate S foliar standing crop T sampling interval

Measuring kelp standing crop Measure foliar standing crop of kelp in meters done monthly in permanent plots at three kelp forests Calculate standing crop of dry kelp in kilograms estimated from length vs. mass relationships of plants collected from our study sites

Measuring growth in giant kelp Estimated monthly as the change in foliar standing crop over the sampling interval plus losses g specific growth rate S foliar standing crop T Sampling interval l loss rate

Measuring kelp losses Measure Frond Loss Rates follow fate of tagged fronds over time Measure Plant Loss Rates estimated from change in density of marked plants in fixed plots +

Macrocystis Foliar Standing Crop

Wave disturbance results in loss of individual fronds and entire plants FrondsPlants r 2 = 0.568, P < r 2 = 0.242, P < 0.003

Recruitment

High Standing CropLow Recruitment Data are monthly means from 3 sites

Growth Rate

Nutritional status of kelp depends on the supply of nutrients r 2 = 0.42, P <0.001 Data are monthly means from 3 sites

Growth rate unrelated to nutrient supply r 2 = 0.046, P < Data are seasonal means from 3 sites

Growth rate unrelated to the nutritional status of kelp r 2 = 0.007, P < Data are seasonal means from 3 sites

High Standing CropLow Growth Rate r 2 = 0.239, P < Data are seasonal means from 3 sites

Growth Rate vs. Foliar Standing Crop

Growth rate influenced by age structure of Foliar Standing Crop (FSC) r 2 = 0.199, P < Collectively, FSC and age structure explained ~ 30 % of variation in growth rate

Net Primary Production

r 2 = 0.47, P < r 2 = 0.62, P < Positively related to density of plants that recruited during the year Positively related to foliar standing crop at the beginning of the year Data are annual means from 3 sites Sources of inter-annual variation in NPP

r 2 = 0.021, P < Data are annual means from 3 sites Annual NPP unrelated to annual growth rate Sources of inter-annual variation in NPP

Initial foliar standing crop and annual recruitment explained 84 % of the inter-annual variation in NPP

r 2 = 0.35, P < r 2 = 0.58, P < Negatively related to loss rates in the preceding autumn Positively related to the previous year’s NPP Data are annual means from 3 sites Sources of inter-annual variation in initial Foliar Standing Crop

Previous year’s NPP & preceding autumn’s loss rate explained 80 % of the inter-annual variation in initial FSC

PulsePress DISTURBANCE FOLIAR STANDING CROP GROWTH NET PRIMARY PRODUCTION PulsePress RESOURCE SUPPLY RECRUITMENT Yet to be shown Shown by others Environmental drivers & biological sources of inter-annual variation in kelp NPP Shown by this study ? -

Environmental drivers of coastal marine ecosystems nutrients Climate acidification sea level temperature wave disturbance Extraction commercial fishing Non-renewable resources recreational fishing Land use runoff pollution eutrophication sedimentation

LINKING SOCIAL & ECOLOGICAL SYSTEMS Ecosystem function Biotic structure Human behavior Ecosystem services Long-term “press” Short-term “pulse” Human outcomes Environmental drivers

Ecosystem function Biotic structure Human behavior Ecosystem services Long-term “press” Short-term “pulse” Human outcomes Environmental drivers LINKING SOCIAL & ECOLOGICAL SYSTEMS

Ecosystem Services Provided by Giant Kelp Forests Cultural Services Education Recreation Aesthetics Tourism Provisioning Services Fisheries Aquaculture Pharmaceuticals Biochemicals Regulating Services Biodiversity conservation Water quality Modify sea surface state

Red sea urchin roe fishery (data from Pt. Loma) Changes in biotic structure and function affect ecosystem services El Niño

Ecosystem function Biotic structure Human behavior Ecosystem services Long-term “press” Short-term “pulse” Human outcomes Environmental drivers LINKING SOCIAL & ECOLOGICAL SYSTEMS

Construction Living resources Boat building Minerals Tourism & Recreation Transportation California’s Ocean Economy Direct Market Value = $21.4 Billion

Competing Ecosystem Services Southern sea otter “Keystone species” Provisioning Services Fisheries Oil and gas development Cultural Services Tourism Education Aesthetics Regulating Services Water quality Conservation

California Sea Otter Population Hunted to near extinction for their fur in the 1800’s Recovery linked to regulatory changes Gill net fishing restrictions Additional fishing restrictions Fur hunting banned

Ecosystem function Biotic structure Human behavior Ecosystem services Long-term “press” Short-term “pulse” Human outcomes Environmental drivers LINKING SOCIAL & ECOLOGICAL SYSTEMS

Defines the "coastal zone" and establishes land use control for the zone California Coastal Act Competing Ecosystem Services Lead to Controversial Legislation Establishes a new isolated population of sea otters at an offshore island and restricts the expansion of sea otters along the mainland Requires the state Department of Fish and Game to design and manage an improved network of marine protected areas

Channel Islands Marine Reserve Channel Islands Marine Reserve Established Biomass of giant kelp in Bed 115 _ N. Santa Rosa Island Data from ISP Alginates Evaluating Ecosystem Change in Response to Environmental Policy Bed 115

Channel Islands Marine Reserve Established Data from ISP Alginates Evaluating Ecosystem Change in Response to Environmental Policy Biomass of giant kelp in Bed 115 _ N. Santa Rosa Island Channel Islands Marine Reserve Channel Islands Marine Reserve Established Bed 115

? Monthly values for the PDO index: 1900 – October 2006 ? warm cool Changes in Policy Coincide with Changes in Environmental Drivers Marine Life Protection Act enacted Santa Barbara Channel Islands Marine Reserve Established

Changes in Policy Coincide with Changes in Environmental Drivers Channel Islands Marine Reserve Established Density of black surfperch at Santa Cruz Island Data from SBC LTER warm PDO cool PDO?

Role of Long Term Research in Society and the Environment Long-term data are needed to understand patterns and causes of changing ecosystems Such knowledge is essential for evaluating the effectiveness of policies enacted to alter human behaviors that influence environmental drivers of ecosystems and the services that they provide