Marine Ecology Progress Series : celebrating 40 years of global impact

The first issue of Marine Ecology Progress Series (MEPS) was published on July 30th, 1979. By the end of that year the first volume (Issues 1 to 4) included an impressive 46 papers authored by scientists representing na tions from Europe, North America, Asia and Africa. Although German and US scientists led the majority (61%) of articles in Vol. 1, MEPS quickly grew into a global journal (Fig. 1). This diversity of authorship is matched by the wide breadth of topics embraced in each and every volume (from bacteria and fora minifera to jellyfish and sharks, from singlespecies studies in the laboratory and the wild to ex tensive community-level field research, sometimes over de cades). To help celebrate MEPS’ auspicious 40th birth day in 2019 and look back on the broad impact of MEPS on the field of marine ecology, we briefly present and describe the unique contributions by MEPS’ 40 most highly-cited studies — the ‘MEPS Top 40 at 40’ (Table 1).


INTRODUCTION
The first issue of Marine Ecology Progress Series (MEPS) was published on July 30th, 1979.By the end of that year the first volume (Issues 1 to 4) included an impressive 46 papers authored by scientists representing na tions from Europe, North America, Asia and Africa.Although German and US scientists led the majority (61%) of articles in Vol. 1, MEPS quickly grew into a global journal (Fig. 1).This diversity of authorship is matched by the wide breadth of topics embraced in each and every volume (from bacteria and fora minifera to jellyfish and sharks, from singlespecies studies in the laboratory and the wild to extensive community-level field research, sometimes over de cades).To help celebrate MEPS' auspicious 40th birth day in 2019 and look back on the broad impact of MEPS on the field of marine ecology, we briefly present and describe the unique contributions by MEPS' 40 most highly-cited studies -the 'MEPS Top 40 at 40' (Table 1).

EXPERIMENTAL DESIGN AND ANALYSIS
Some of the most highly-cited studies within MEPS introduced statistical techniques that are now commonplace when designing field studies and/or analyzing ecological data.These techniques include sampling designs appropriate for testing differences among field locations (Clarke & Green 1988) and the use of multi-dimensional scaling in revealing patterns in distribution among field stations to help identify environmental drivers or indicator species (Field et al. 1982, Clarke & Ainsworth 1993).Other well-cited studies introduced biodiversity indices (e.g.Delta, Delta* or variation in taxonomical distinctness) (Warwick & Clarke 1995, Clarke & Warwick 2001), which have become mainstays in research examining ecosystem change along environmental gradients.

NEW MEASUREMENT TECHNIQUES
Papers unveiling powerful measurement techniques that greatly advanced marine ecology are also among some of the most highly-cited papers in MEPS.In order to advance studies of nutrient cycling, Hoppe (1983) introduced a technique to measure in situ enzymatic degradation of macromolecules, a key step controlling the rate of production of dissolved organic carbon.Several studies reported improvements in the chemical measurement of algal pigments (Wright et al. 1991, Mackey et al. 1996, Zapata et al. 2000), paving the way for more precise estimates of standing stocks of different phytoplankton groups.In order to enhance understanding of food web structure, Hobson & Welch (1992) used measurements of stable-carbon and -nitrogen isotope ratios in the Arctic to create a novel isotopic food web model.A few years later, by summarizing and com-paring 876 values of Carbon-13, France (1995) documented differences between marine and freshwater taxa and between phytoplankton and benthic algae in marine habitats.In reviewing chemical measurements on fish otoliths, calcium carbonate ear bone structures containing growth rings, Campana (1999) demonstrated the wealth of information that these structures could provide on the life history of individuals, including stage-specific habitat utilization.This approach played a central role in launching a wide range of studies on population connectivity, a major research challenge in basic marine ecology and in fisheries management.

FUNDAMENTAL ECOLOGY OF ORGANISMS AND COMMUNITIES
The field of marine ecology requires fundamental understanding of the trophodynamic structure and function of marine ecosystems, nowadays a prevalent research theme in studies published in MEPS.In MEPS' most highly-cited article, Azam et al. (1983) described the roles of water-column bacteria and microplankton such as heterotrophic flagellates in the 'microbial loop'.Subsequent work described specific aspects of the 'microbial loop' such as bacterial protein synthesis (Simon & Azam 1989) and generated relationships for predicting bacterial production in the water column and sediments in different marine and freshwater systems (Cole et al. 1988).Funda-mental MEPS studies also advanced knowledge on the growth physiology and life-cycle dynamics of key groups of planktonic and benthic organisms that helped set future research directions.This includes research on (1) phytoplankton nutrient requirements (Dortch 1990, Egge & Aksnes 1992), (2) the metabolic and lipid dynamics of zooplankton (Kiørboe et al. 1985, Lee et al. 2006), and (3) larval dynamics and the process of settlement and recruitment in benthic invertebrates (Gosselin & Qian 1997, Hunt & Scheibling 1997, Pechenik 1999).Three well-cited papers revealed fundamental aspects of coral ecology including how (1) reef-building corals reproduce using fragmentation (Highsmith 1982), (2) healthy corals have a rich, species-specific bacterial community (Roh wer et al. 2002) and (3) the mucus of corals contains antibiotic protection against invasive microbes (Ritchie 2006).Fish ecological research documented species-specific patterns of trophic niche breadth and size-based feeding strategies (Scharf et al. 2000).Other papers provided novel comments and syntheses on key processes such as epibiosis (Wahl 1989), top-down control (Verity & Smetacek 1996), and the nursery function of ecosystem engineers such as seagrasses (Heck et al. 2003).

MARINE ECOLOGY IN THE ANTHROPOCENE
Across 4 decades marked by increasing anthropogenic pressures, MEPS documented impacts of  For example, studies highlighted the deleterious impacts of (1) eutrophication on coastal habitats (Cloern 2001, Gray et al. 2002, Kemp et al. 2005), (2) sedimentation and the destruction of coral habitats (Rogers 1990), and (3) fishing on benthic and pelagic invertebrate and fish communities (Friedlander & DeMartini 2002, Kaiser et al. 2006, Lester et al. 2009).
Three studies discussed impacts of ongoing ocean acidification on invertebrates and/or fish (Michaelidis et al. 2005, Kurihara 2008, Pörtner 2008), while another study reflected on how interaction of various anthropogenic stressors may have increased jellyfish populations world-wide with substantial economic costs to human communities (Purcell et al. 2007).

HORIZONS IN MARINE ECOLOGY
Against this backdrop of highly-cited research on such a wide range of subjects, we are pleased to announce that, to celebrate its 40 th anniversary, MEPS plans to publish a number of perspective articles written by recognized leaders in different fields of marine ecology.Each Ecological Memoir will cover a specific topic (from marine microbes to marine management), chronicling how the field has advanced and providing an outlook on the most exciting developments and future avenues of re search in that area.We hope that our readers will find these articles interesting and inspiring, especially the students and early career researchers who will produce the next 40 years of outstanding marine ecological research.
Fig. 1.A global view of MEPS' authorship based on the country affiliation of authors of published manuscripts.The cumulative number is shown for papers published between 1997 and 2018 (Vol.156 to 604)

Table 1 .
The cumulative number is shown for papers published between1997 and 2018 (Vol.156 to 604)The 40 most-cited articles published in MEPS.Numbers of citations are based on a search performed on 25th October 2018 using CrossRef data.This dataset underestimates full citation numbers, typically by a factor of about 2 (only citation counts of participating publishing outlets are included), but was selected over other data sources such as Google Scholar because of its reliability for comparison purposes human activities on marine species, communities, and ecosystems.The first volume of MEPS contained several studies documenting impacts of environmental stressors (e.g.hypoxia, oil, metals) on the vital rates of marine fauna.Not surprisingly, therefore, our Top 40 contain seminal research efforts documenting aspects of the human footprint on marine habitats.